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GASOLOGY 


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GASOLOGY 


BEING  A  REPRINT  FROM  THE 

GAS  ENGINE  COURSE  OF 

GAS  REVIEW 


PUBLISHED  BY 

GAS  REVIE  w 

I! 

MADISON,  WISCONSIN 


\ 


Copyright,  1910 

By 
We  American  Ghresherman 


FOREWORD 


This  little  volume  is  a  compilation  of  the  first  twenty- 
seven  lessons  of  the  "Gas  Engine  Course"  which  has  been 
published  as  a  serial  in  Gas  Review. 

When  Gas  Review  first  started  three  years  ago  it  was 
deemed  advisable  to  offer  a  complete  course  in  gas  and  gas- 
oline engineering.  One  requirement  of  these  lessons  was 
that  they  were  to  be  written  in  plain,  simple  language  that 
anyone  could  understand.  We  have  followed  that  idea  all 
the  way  through  and  the  lessons  won  the  approval  of  our 
readers  from  the  start. 

There  were  many  calls  for  back  copies  of  Gas  Review 
from  those  who  subscribed  late  and  who  wanted  to  own  a 
complete  copy  of  the  lessons  and  we  concluded  to  publish 
them  in  book  form  since  we  were  unable  to  supply  back 
copies  of  the  magazine. 

The  lessons  do  not  cover  the  whole  subject  for  the  reason 
that  they  are  not  yet  completed.  However,  as  far  as  they 
have  gone  they  cover  the  subject  quite  completely  and  it  is 
believed  will  give  the  reader  much  valuable  information  in 
regard  to  the  best  modern  practice. 

We  have  drawn  freely  from  many  sources  in  preparing 
the  lessons  and  make  no  claims  for  originality  in  anything 
except  the  phraseology  and  general  arrangement  of  the  sub- 
ject matter.  In  these  particulars  we  believe  we  have  suc- 
ceeded in  producing  a  book  that  has  the  great  merit  of 
clearness  and  simplicity.  It  is  a  book  primarily  for  the 
beginner  and  the  actual  user. 


CONTENTS 

CHAPTEE  I. — GAS  ENGINE  PRINCIPLES. 

Explanation  of  the  events  in  a  four-cycle  engine;  comparison  of  gas  en- 
gine and  steam  engine;  transformation  of  heat  into  useful  work;  heat  units; 
chemistry  of  combustion;  proportions  of  the  fuel  mixture;  timing  of  igni- 
tion; simple  methods  of  cooling  the  cylinder;  laws  governing  pressure,  vol- 
ume and  temperature  of  a  gas. 

CHAPTER  II.— IGNITION. 

Methods  of  ignition;  description  of  the  hot  tube  system;  ignition  by  com- 
pressing the  charge;  systems  of  electric  ignition;  electrical  terms  defined; 
kinds  of  batteries;  action  of  simple  primary  cell;  polarization;  Edison  Le 
Lande  cell;  arrangement  of  cells;  construction  and  chemical  action  of  dry 
cells. 

CHAPTEE  III. — MAGNETISM  AND  COILS. 

Magnetos;  magnetism  and  magnetic  lines  of  force;  electro-magnetic  in- 
duction; the  kick  coil;  jump  spark  coil  with  vibrator;  induction;  condensers. 

CHAPTEE  IV.— DYNAMO — ELECTRIC  GENERATORS. 

How  an  electric  current  is  generated;  description  of  simple  generator; 
the  action  of  a  magneto;  high  tension  and  low  tension  magnetos;  magneto 
troubles;  testing  and  repairing  a  magneto. 

CHAPTEE  V. — STORAGE  BATTERIES. 

The  elements  and  the  electrolyte;  explanation  of  chemical  reactions; 
charging  a  storage  battery;  charging  from  a  lighting  circuit;  the  rating  of 
storage  batteries;  laying  up  a  battery. 

CHAPTEE  VI. — WIRING  AN  ENGINE. 

Cells  connected  in  series,  in  multiple,  in  series  multiple;  simple  make  and 
break  ignition;  description  of  timer;  wiring  single  cylinder  engine  using 
battery  and  jump  spark;  same  with  two  batteries;  wiring  two-cylinder  ver- 
tical engine — jump  spark — using  two  batteries;  same  for  two-cylinder  op- 
posed engine — one  coil — dry  cells  and  storage  battery;  wiring  for  four- 
cylinder  engine  using  battery;  same  with  one  coil  and  distributer;  wiring 
multi- cylinder  engine  with  magneto;  same  with  magneto  and  battery. 

CHAPTEE  VII. — ENGINE  BALANCE. 

Methods  of  balancing  a  single  cylinder  engine;  effect  of  fly  wheels;  ar- 
rangement of  cranks  in  multi-cylinder  engines;  the  order  of  firing;  effect 
of  rotating  and  of  reciprocating  parts. 

CHAPTEE  VIII.— CARBURETORS. 

Carburetion  defined;  proportion  of  air  to  gasoline  required;  principles  of 
carburetion;  effect  of  faulty  mixtures;  action  of  the  spray  carburetor;  dif- 
ferent forms  of  spray  carburetors ;  types  of  carburetors ;  action  of  float  feed 
carburetors;  automatic  carburetors;  examples  of  modern  carburetors. 

CHAPTEE  IX. — HORSE  POWER  FORMULAS. 

How  work  is  measured;  horse  power;  formulas  for  figuring  horse  power; 
gas  engine  efficiency. 


CHAPTER  I 

GAS  ENGINE  PRINCIPLES 


LESSON  I. 

In  presenting  this  series  of  lessons  on  the  gas  engine,  the  aim  will 
be  to  explain  as  clearly  as  possible  the  principles  of  action  of  each 
type  considered,  the  various  mechanisms  by  which  the  engine  is  en- 
abled to  perform  its  operations,  together  with  directions  in  regard  to 
the  care  and  proper  method  of  handling  gas  engines. 

Very  little  attention  will  be  given  to  the  principles  of  designing 
and  the  computations  necessary  for  the  proportioning  of  the  various 
parts.  Neither  will 
much  attention  be 
given  to  the  mathe- 
matical theory  of  the 
gas  engine  beyond 
what  can  be  worked 
out  by  the  simpler 
rules  of  arithmetic. 
The  aim  of  these 
lessons  is  to  help 

those  who  are  running  gas  engines,  rather  those  who  are  designing 
them.    To  this  end  the  lessons  will  be  rather  elementary  in  character. 

The  term  gas  engine  is  commonly  applied  to  any  engine  in  which 
the  fuel  is  first  turned  into  a  gaseous  state  and  then  burned  in  the  en- 
gine cylinder.  Gasoline  engines,  kerosene  engines,  crude  oil  engines 
and  alcohol  engines  are  all  called  gas  engines,  as  well  as  those  that  run 
on  either  city  gas  or  producer  -gas.  A  better  appellation  for  such 
engines  and  one  that  is  now  frequently  applied  is  "internal  combus- 
tion engines." 

The  general  principles  governing  both  the  construction  and  the 
operation  of  a  gas  engine  are  nearly  the  same  as  in  a  steam  engine. 
The  object  in  both  is  to  obtain  useful  work  from  heat,  that  is,  to 
transform  heat  energy  into  work.  In  the  steam  engine  fuel  is  burned 
in  a  furnace  under  a  boiler  which  contains  water.  The  water  is 
heated  to  the  boiling  point  and  steam  is  formed.  This  steam  is  piped 
to  the  cylinder  of  an  engine  and  is  there  made  to  push  a  piston  back 
and  forth  and  rotate  a  shaft  which  is  connected  therewith  by  suitable 
connectors.  In  the  steam  engine,  therefore,  there  are  three  distinct 

218577 


GASOLOGY. 


parts,  the  furnace,  the  toiler  and  the  engine — the  two  latter  may  be 
close  together,  or:  at  a  considerable  distance  from  each  other  and  con- 
nected by  means  of  a  steam  pipe.  In  any  event,  the  source  of  heat  and 
the  moving  piston  are  at  a  considerable  distance  apart,  with  the  boiler 
intervening. 

In  the  case  of  the  gas  engine  the  transformation  of  heat  into  work 
is  accomplished  in  a  simpler  and  more  nearly  direct  manner.  The 
fuel,  together  with  the  necessary  air  for  combustion,  is  introduced  di- 
rectly into  the  engine  cylinder  where  it  is  burned.  The  gases  or  smoke 
resulting  from  this  burning  of  the  fuel  are  raised  to  a  very  high  tem- 
perature, estimated  at  from  two  thousand  to  three  thousand  degrees 
Fahrenheit.  This  high  temperature  causes  the  pressure  of  the  gases  to 
rise  and  provides  the  motive  force  for  moving  the  piston. 

In  both  the  steam  engine  and  the  gas  engine  heat  is  the  motive 
force.  In  both,  heat  is  applied  to  a  gaseous  substance  in  order  to  raise 
its  pressure  and  do  work.  In  the  former  the  gas  is  steam,  in  the  lat- 
ter it  is  smoke  resulting  from  the  combustion  of  the  charge  of  fuel 
introduced  into  the  cylinder.  The  similarity  in  the  principles  of  op- 
eration of  the  two  types  of  engines  has  thus  been  pointed  out,  and  it  is 
quite  evident  that  of  the  two  the  gas  engine  is  the  simpler.  It  ought 
also  to  be  more  efficient,  that  is,  it  ought  to  transform  a  larger  amount 
of  heat  energy  of  the  fuel  into  work  than  the  steam  engine  because  of 
its  simplicity,  and,  as  a  matter  of  fact,  it  does.  The  average  steam 
engine  can  only  turn  from  five  to  ten  per  cent  of  the  heat  energy  of 
the  fuel  into  work,  while  an  ordinary  gas  engine  utilizes  from  twelve  to 
twenty-five  per  cent.  Despite  the  difference  in  efficiency,  however,  the 

steam  engine  possesses 
certain  advantages  in 
operation  that  make  it 
a  more  desirable  form 
of  motor  for  many 
kinds  of  work  than  the 
gas  engine,  while  for 
certain  other  purposes 
the  gas  engine  is  with- 
out a  rival. 


$        Ccmpnititf   if 
\        the  clacft 

! 

\   \.  5* 

FIG.  2. 


Before  going  further  into  the  matter  of  efficiencies  or  advantages 
of  the  different  types  of  heat  engines,  we  will  first  discuss  the  ele- 
mentary mechanism  of  a  gas  engine. 

Every  gas  engine,  no  matter  whether  it  uses  alcohol,  gasoline,  kero- 
sene or  some  other  gaseous  or  liquid  fuel,  must  have  certain  parts,  no 
matter  how  different  engines  may  vary  in  other  details.  These  parts 
are  shown  diagramatically  in  the  four  accompanying  sketches — Figs, 


GAS  ENGINE  PRINCIPLES. 


1,  2,  3  and  4,  with  all  the  parts  named.  The  type  of  engine  illustrat- 
ed is  called  the  four-stroke  cycle  engine  or  sometimes-,  simply  the 
four  cycle  engine,  since  four  separate  strokes  of  the  piston  are  nec- 
essary to  complete  its  cycle  of  operation.  There  is  another  type  of 
engine  which  completes  its  entire  cycle  in  two  strokes,  or  one  revo- 
lution of  the  crank  shaft,  called  a  two-stroke  cycle  engine. 

Referring  to  Fig.  1,  it  will  be  noticed  that  the  length  of  the  cylin- 
der is  considerably  greater  than  the  length  of  the  stroke  and  of  the 
piston  combined.  When  the  piston  is  at  the  left  end  of  the  cylinder 
there  is  still  left 
a  considerable  space 
between  the  piston 
and  the  cylinder 
head.  This  space  is 
sometimes  called  the 
clearance,  sometimes 
the  compression 
chamber  and  some- 
times the  explosion 


FIG.  3. 


chamber,  since  it  performs  all  three  of  these  functions.  Both  the 
inlet  valve  and  the  exhaust  valve  are  located  in  this  chamber  and  both 
open  inward.  When  the  piston  moves  toward  the  right  from  its 
extreme  inner  position,  a  charge  of  fuel  and  air,  which  has  been 
first  mixed  in  the  proper  proportions,  is  drawn  in  through  the  inlet 
valve,  while  at  the  same  time  the  exhaust  valve  is  held  shut. 

On  the  return  stroke  of  the  piston,  shown  in  Fig.  2,  both  valves  re- 
main closed  and  the  charge  is  forced  back  and  compressed  in  the  com- 
pression chamber.  The  amount  of  compression  varies  according  to  the 
size  of  the  chamber  in  the  various  makes  of  engines  and  according 
to  the  fuel  used,  but  may  be  taken  roughly  as  being  from  fifty  to  one 
hundred  and  fifty  pounds  per  square  inch.  Just  before  reaching 

the  inner  dead  cen- 
ter, the  charge  is  ig- 
nited, combustion  or 
explosion  takes  place, 
and  the  piston 
starts  toward  the 
right  again,  as 
shown  in  Fig.  3. 

T-,  During    this    stroke 

-C IG.  4.  i     ,1  n 

both    valves    remain 

closed  until  almost  at  the  end  of  the  stroke,  when  the  exhaust  valve 
is  forced  open  and  the  spent  charge  is  allowed  to  escape.  During 
the  fourth  stroke,  see  Fig.  4,  the  exhaust  valve  remains  open  and  the 


8  GASOLOGY. 

burnt  gases  are  forced  out  of  the  cylinder  by  the  retreating  piston.  Just 
previous  to  the  end  of  this  stroke  the  exhaust  valve  snaps  shut  and 
on  the  fifth  stroke  a  new  charge  is  drawn  in,  thus  beginning  a  new 
cycle  of  operations,  and  subsequently  the  whole  series  of  operations 
is  repeated  indefinitely  and  automatically  as  long  as  the  mechanism 
is  in  running  order. 

While  the  above  parts  are  essential  to  every  gas  engine,  it  will  be 
understood,  of  course, 'that  an  engine  so  constructed  would  not  run. 
There  are  other  parts  and  details  necessary  to  a  complete  working  en- 
gine, all  of  which  will  be  taken  up  and  described  in  subsequent  les- 
sons. 

* 

LESSON  II. 

The  gas  engine,  like  the  steam  engine,  is  a  heat  motor.  It  trans- 
forms heat  into  mechanical  energy.  Consequently,  to  be  in  any  meas- 
ure complete,  a  study  of  the  gas  engine  must  include  a  study  of  the 
laws  of  heat. 

Heat  is  not  a  substance  but  a  condition.  It  has  been  defined  as  a 
form  of  energy.  When  a  body  is  hot  all  of  its  particles  or  molecules 
are  in  a  rapid  state  of  vibration;  the  hotter  it  is  the  more  rapid  the 
vibration.  As  it  cools,  the  particles  move  less  and  less  rapidly  and 
through  shorter  distances,  thus  causing  the  body  to  contract.  There 
is  a  difference  between  temperature  and  quantity  of  heat.  Tempera- 
ture merely  measures  the  intensity  of  heat  and  not  the  amount.  For 
example,  if  a  small  rod  of  iron  be  heated  red  hot  and  then  be  plunged 
into  a  barrel  of  water,  it  will  lose  its  heat  to  the  water  without  raising 
have  absorbed  all  the  heat  of  the  iron  down  to  its  own  temperature, 
the  temperature  of  the  water  a  perceptible  amount.  Yet  the  water  will 

In  order  to  measure  quantity  of  heat,  a  unit  of  measurement  has 
been  adopted  by  engineers,  called  the  British  Thermal  Unit — generally 
written  in  engineering  work  simply  B.  t.  u.  A  B.  t.  u.  may  be  defined 
as  the  amount  of  heat  necessary  to  raise  one  pound  of  water  from 
sixty-two  to  sixty-three  degrees  F.  The  heating  of  two  pounds  of 
water  through  the  same  range  of  temperature  requires  two  heat  units 
and  so  on.  Water  is  taken  as  the  measuring  substance  because  it  ab- 
sorbs more  heat  for  a  certain  weight  than  almost  anything  else. 

There  is,  as  foreshadowed  in  the  first  part  of  this  lesson,  a  definite 
relation  between  heat  and  work.  Careful  experiments  have  proven 
that  a  heat  unit  is  equal  in  mechanical  energy  to  778  foot  pounds. 
That  is,  the  amount  of  heat  necessary  to  heat  one  pound  of  water  one 
degree  is  equivalent  to  raising  a  weight  of  778  pounds  one  foot  high, 
or,  what  is  the  same  thing,  raising  one  pound  778  feet  high. 


GAS  ENGINE  PRINCIPLES.  9 

The  reader  may  inquire  at  this  point  what  the  above  conception  of 
heat  has  to  do  with  a  gas  engine.  The  answer  is  easily  given.  A 
pound  of  fuel  contains  a  certain  number  of  B.  t.  u.  and  since  it  is  the 
duty  of  the  engine  to  transform  them  into  work,  it  follows  that  if  we 
want  to  find  out  just  how  efficient  an  engine  is  we  must  measure  the 
number  of  heat  units  supplied  in  the  form  of  fuel  and  then  determine 
how  many  of  these  heat  units  have  been  turned  into  useful  work  at 
the  band  wheel.  To  illustrate,  every  pound  of  gasoline  contains  from 
18,000  to  20,000  B.  t.  u.  If  on  testing  an  engine  we  found  that  for 
every  pound  of  gasoline  used  we  obtained  the  value  of  4,500  to  5,000 
B.  t.  u.  in  useful  work,  then  the  actual  heat  efficiency  of  the  engine 
would  be  twenty-five  per  cent.  That  is,  one-quarter  of  the  heat 
producing  power  of  the  gasoline  was  turned  into  useful  work  and 
three-quarters  was  lost.  That  which  is  lost  is  carried  away,  in 
part  by  the  jacket  water,  in  part  by  the  exhaust  gases,  while 
the  remainder  is  lost  in  overcoming  the  friction  of  the  engine 
and  through  radiation.  A  complete  test  of  an  engine  takes  account  of 
all  these  losses  and  if  the  engineer  who  makes  the  tests  understands  the 
laws  of  heat,  he  can  determine  very  closely  just  how  much  is  lost  in 
each  of  the  different  ways  above  mentioned.  A  complete  discussion 
of  the  laws  of  heat  will  be  reserved  for  a  future  lesson  when  directions 
will  be  given  for  making  a  complete  test. 

We  will  now  proceed  to  discuss  some  of  the  effects  of  heat.  The 
general  effect  of  heating  a  body  is  to  cause  it  to  expand.  If  a  gas, 
such  as  air,  is  heated  it  expands,  or  if  it  is  imprisoned  so  that  it  can- 
not expand,  it  exerts  a  pressure  on  the  walls  of  the  containing  vessel 
in  proportion  to  its  absolute  temperature.  The  absolute  temperature, 
by  the  way,  is  measured  from  absolute  zero,  that  is,  a  point  461  de- 
grees below  zero  on  the  Fahrenheit  scale  and  is  the  point  at  which  all 
molecular  motion  ceases.  Above  that  temperature  all  the  bodies  are 
supposed  to  contain  some  heat  and  their  particles  are  in  a  state  of 
motion.  The  expansion  or  rise  in  pressure  of  a  gas  when  heated  is 
the  principle  that  is  taken  advantage  of  in  a  gas  engine. 

As  explained  in  lesson  I,  a  charge  is  drawn  into  the  cylinder  and 
there  compressed.  At  the  moment  when  the  piston  is  passing  center 
the  charge  is  ignited  and  burned,  the  temperature  of  the  resulting  gas 
is  raised  to  between  2,000  and  3,000  F.,  and  since  this  gas  is  imprisoned 
behind  the  piston  in  a  small  space  it  exerts  a  tremendous  pressure  upon 
the  piston  at  the  beginning  of  the  stroke.  The  amount  of  the  pressure 
varies  under  different  conditions  of  adjustment  of  the  engine  and 
upon  the  amount  of  fuel  and  air  admitted  to  the  cylinder  and  the 
proportion  in  which  the  two  are  mixed.  In  ordinary  gas  engines  the 
pressure  often  amounts  to  350  or  400  pounds  per  square  inch,  thus 


10  GASOLOGY. 

giving  a  total  pressure  on  an  eight-inch  piston  of  somewhere  near 
20,000  pounds.  This  pressure,  it  must  be  borne  in  mind,  is  not  in  the 
nature  of  a  blow  such  as  would  be  struck  with  a  heavy  hammer,  but  to 
the  sudden  energy  imparted  to  the  gases  by  the  liberation  of  the  heat 
energy  of  the  fuel  they  contain  when  first  admitted  to  the  cylinder. 
As  the  piston  advances  on  its  power  stroke  the  gases  expand  and  this 
pressure  falls  rapidly  until  at  the  end  of  the  stroke  when  the  ex- 
haust valve  opens,  the  pressure  is  comparatively  small.  On  account 
of  the  very  high  initial  pressure,  however,  the  average  pressure  for  the 
whole  stroke  is  quite  high,  as  it  must  be  considering  the  fact  that 
there  is  only  one  power  stroke  in  every  four  strokes  of  the  piston. 

Since  the  motive  power  of  the  engine  is  heat  and  this  heat  is  gen- 
erated by  the  combustion  of  fuel  in  the  engine  cylinder,  it  follows,  nat- 
urally, that  a  knowledge  of  the  principles  of  combustion  is  essential 
to  a  proper  understanding  of  the  working  of  a  gas  engine.  The  lack 
of  understanding  of  this  important  subject  is  responsible  for  a  con- 
siderable amount  of  the  difficulty  in  handling  these  engines. 

Combustion  or  burning  is  a  chemical  process  and  may,  for  our  pur- 
poses, be  defined  as  .a  combination  with  oxygen.  The  oxygen  is  sup- 
plied by  the  air,  which  consists  of  two  gases,  oxygen  and  nitrogen, 
mixed  in  the  proportion  of  786  parts  of  nitrogen  and  214  parts  of  oxy- 
gen, by  volume.  When  fuel  burns,  the  oxygen  of  the  air  unites  with 
the  carbon  and  hydrogen  in  the  fuel,  forming  a  new  chemical  com- 
pound. This  compound  is  in  the  form  of  a  gas  and  is  the  resulting 
smoke  of  combustion.  The  liquid  fuels,  such  as  gasoline,  kerosene 
and  alcohol,  are  composed  of  carbon  and  hydrogen  in  varying  propor- 
tions, depending  upon  the  fuel  used.  When  they  are  introduced  into 
an  engine  cylinder  they  are  mixed  with  the  proper  amount  of  air  in  a 
chamber  called  a  carburetor,  from  which  they  pass  directly  to  the 
engine  cylinder.  When  the  charge  of  air  and  fuel  passes  into  the 
cylinder  the  fuel  is  either  in  the  form  of  a  gas  or  vapor  or  else  in  a 
very  finely  divided  mist  or  fog. 

Ignition  is  started  by  passing  a  flame  through  some  portion  of  the 
charge,  as  in  the  case  of  the  electric  spark  or  by  means  of  a  heated 
body.  The  gas  at  this  place  is  heated  to  the  ignition  point  and  the 
resulting  flame  rapidly  propagates  itself  throughout  the  mass. 

A  certain  amount  of  carbon  requires  a  definite  quantity  of  oxygen 
for  complete  combustion  and  the  same  is  true  of  the  hydrogen. 
Consequently  the  fuel  and  air  must  be  mixed  in  exactly  the  right  pro- 
portions to  give  the  best  results.  If  too  much  fuel  is  supplied  for  the 
amount  of  air,  the  mixture  will  be  too  rich  in  fuel  and  ignition  may 
not  take  place  at  all,  and  if  it  does  the  heat  generated  will  not  be  as 
great  as  though  the  correct  proportion  were  used.  Consequently  the 


GAS  ENGINE  PRINCIPLES.  11 

engine  will  not  develop  its  maximum  power.  On  the  other .  hand, 
if  there  is  not  enough  fuel  for  the  amount  of  air  admitted,  the  mix- 
ture will  be  lean  and  ignition  may  fail  or  the  explosion  may  be 
weak. 

In  the  greater  number  of  small  engines  using  liquid  fuel,  the  sup- 
ply of  air  cannot  be  varied  and  so  the  correct  mixture  is  obtained  by 
setting  the  oil  valve  to  admit  the  right  amount  of  fuel.  The  correct 
amount  of  fuel  is  determined  by  the  character  of  the  exhaust  gases. 
As  much  fuel  should  be  admitted  as  possible  without  showing  a  dense 
smoke  at  the  exhaust. 

LESSON  III. 

It  was  shown  in  the  last  lesson  that  there  must  be  the  correct  pro- 
portion of  fuel  and  air  in  order  to  obtain  a  mixture  that  will  ignite 
readily  and  burn  to  the  best  advantage.  Such  a  mixture  burns  almost 
instantaneously  and  is  said  to  be  explosive. 

Gun  powder,  dynamite  and  other  such  explosives  differ  from  the 
explosive  mixture  in  a  gas  engine  in  this  particular.  They  do  not 
require  air  to  supply  the  necessary  oxygen  for  their  complete  com- 
bustion because  they  contain  a  chemical  within  themselves  which  sup- 
plies the  necessary  oxygen  in  copious  quantities.  All  fire  arms  are 
gas  engines,  nevertheless,  because  it  is  the  gas  formed  by  the  burn- 
ing of  the  powder  which  hurls  the  missile  from  the  barrel.  This  gas 
which  is  formed  almost  instantly  is  highly  heated  by  the  process  of 
burning  and  exerts  an  enormous  pressure  in  the  gun  barrel  just  as  the 
burning  of  the  charge  in  a  gas  engine  cylinder  causes  pressure  on  the 
piston  and  drives  it  forward. 

Before  any  substance,  either  solid  or  liquid,  can  be  burned  it  must 
be  heated  to  such  a  temperature  that  the  carbon  and  hydrogen  which 
it  contains  are  distilled  from  the  surface  in  a  gaseous  form.  The 
temperature  at  which  any  substance  will  ignite  is  called  the  ignition 
point,  and  this  temperature  is  that  at  which  the  given  substance  be- 
gins to  give  off  a  gas.  A  lump  of  coal  does  not  burn  as  a  solid  but  as 
a  gas.  Likewise,  kerosene,  gasoline  and  alcohol  and  other  liquids 
used  in  gas  engines  must  also  be  turned  into  a  gas  before  they  will 
become  readily  explosive.  Gasoline  at  ordinary  temperatures  forms 
a  gas  and  it  is  therefore  easy  to  start  an  engine  with  this  fuel  except 
in  very  cold  weather.  When  the  weather  is  severe  heat  must  be  ap- 
plied at  some  point  in  order  to  start,  either  to  the  engine  cylinder  by 
filling  the  jacket  with  hot  water,  to  the  air  by  heating  the  air  pipe  or 
mixer  with  a  torch  or  a  piece  of  hot  iron,  or  by  heating  the  gasoline. 
The  latter  method  is  somewhat  dangerous  and  is  not  recommended. 
Kerosene  and  alcohol  both  form  a  gas  at  higher  temperatures  than 


1 2  GASOLOGY. 

gasoline  and  consequently  it  is  more  difficult  to  start  an  engine  with 
either  of  these  fuels.  After  getting  the  cylinder  warmed  up  by  us- 
ing gasoline  to  start  with,  however,  kerosene  or  alcohol  can  then  be 
used  with  good  success  because  the  heat  within  the  cylinder  walls  is 
then  sufficient  to  transform  the  fine  mist  or  spray  of  the  charge  into  a 
gaseous  form.  While  the  ordinary  gasoline  engine  may  not  run  as 
economically  on  either  of  these  fuels  as  on  gasoline,  still  it  can  be 
made  to  work  quite  satisfactorily. 

In  order  that  a  gas  shall  begin  to  combine  with  oxygen,  that  is, 
to  burn,  it  must  be  set  fire  to,  it  must  be  ignited.  There  are  numer- 
ous ways  in  which  this  may  be  accomplished,  but  the  ordinary  meth- 
od is  by  means  of  an  electric  spark.  The  gas  in  immediate  contact 
with  the  spark  is  heated  to  a  high  temperature  and  a  flame  is  started 
which  travels  through  the  mass  with  great  rapidity,  provided  that  the 
mixture  of  gas  and  air  is  in  the  right  proportions  and  thoroughly 
mixed.  If  the  mixture  is  not  correctly  proportioned  the  flame  will 
travel  slowly  and  combustion  may  not  be  complete.  That  is,  some 
of  the  gas  may  not  be  consumed  when  the  piston  reaches  the  end  of  its 
stroke.  With  the  ordinary  gas  engine  these  conditions  may  not  ob- 
tain either  if  too  much  fuel  is  admitted  or  if  there  is  not  enough. 
In  the  first  case  a  dense  smoke  will  appear  at  the  exhaust,  in  the 
second,  one  or  more  charges  may  mis-fire  and  be  forced  into  the 
muffler,  then  when  a  charge  is  fired  the  hot  gases  coming  in  contact 
with  those  remaining  in  the  muffler  will  cause  an  explosion  at  that 
point.  In  either  the  first  case  or  the  second  the  force  of  the  ex- 
plosion in  the  cylinder  is  weak  and  the  engine  is  not  developing  the 
power  it  should  develop. 

In  the  ordinary  gasoline  engine  the  size  of  the  air  pipe  is  fixed  and 
can  not  be  changed  and  consequently  the  only  way  to  alter  the  mixture 
is  by  adjusting  the  fuel  valve. 

The  timing  of  the  ignition  is  an  important  point  in  the  opera- 
tion of  gas  engines.  In  all  cases  ignition  should  occur  just  before 
the  piston  reaches  dead  center  on  the  compression  stroke.  The  exact 
point  depends  upon  the  character  of  the  gas  and  the  speed  of  the  en- 
gine. Ignition  should  always  occur  early  enough  so  that  the  gas 
will  be  all  burned  by  the  time  the  piston  starts  on  the  power  stroke. 
It  is  a  well  known  fact  that  a  gas  highly  compressed,  or  in  the  act 
of  being  compressed,  burns  more  rapidly  than  when  it  is  not  com- 
pressed or  when  it  is  expanding.  In  the  case  of  a  gas  being  com- 
pressed the  flame  cap  and  the  gas  are  moving  toward  each  other,  while 
if  the  gas  is  expanding  the  flame  cap  must  follow  a  substance  that  is 
rapidly  retreating  before  it.  Consequently,  if  ignition  occurs  just 
when  the  piston  is  at  the  end  of  its  compression  stroke,  or  after  it 


GAS  ENGINE  PRINCIPLES.  13 

has  started  on  its  power  stroke,  ignition  must  necessarily  be  much 
slower  and  it  may  even  happen  that  combustion  will  not  be  com- 
pleted when  the  end  of  the  stroke  is  reached.  It  must  be  borne  in  mind 
also  that  the  act  of  complete  combustion  is  not  instantaneous  but,  on 
the  contrary,  takes  an  appreciable  length  of  time.  This  makes  it  nec- 
essary to  ignite  the  charge  before  the  piston  reaches  the  end  of  its 
compression  stroke.  In  slow  speed  engines  running  at  say  two  hundred 
revolutions  per  minute,  ignition  should  occur  when  the  crank  is  from 
five  to  ten  degrees  below  center.  Engines  having  a  higher  speed  must 
be  ignited  still  earlier,  until  on  very  high  speed  engines,  those  running 
at  speeds  above  one  thousand  revolutions  per  minute,  ignition  must 
occur  just  after  the  crank  passes  half  stroke  or  nearly  forty-five  de- 
grees before  the  crank  reaches  center.  With  rich  fuel  mixtures  com- 
bustion is  more  rapid  than  with  lean  mixtures -and  consequently  igni- 
tion does  not  need  to  occur  quite  so  early. 

There  is  another  factor  that  must  be  taken  into  account  in  the 
timing  of  the  ignition  to  get  the  best  results,  and  that  is  the  tempera- 
ture of  the  gas  when  ignition  occurs.  If  the  gas  is  hot,  almost  at  burn- 
ing temperature,  it  burns  much  more  rapidly  than  when  at  a  lower 
temperature.  In  an  engine  that  is  working  hard,  that  is,  one  that 
misses  very  few  explosions,  it  may  happen  that  the  igniter  will  be 
set  to  give  the  best  results  to  start  with,  but  after  the  engine  has 
worked  for  a  considerable  length  of  time  the  cylinder  will  become 
heated  so  much  that  each  new  charge  becomes  heated  almost  to  the 
burning  point  and  when  the  spark  is  formed  combustion  will  be  almost 
instantaneous,  making  it  necessary  to  retard  the  spark  somewhat  in 
order  to  obtain  the  best  results.  A  heavily  loaded  engine  which  works 
all  right  for  a  time  and  then  begins  to  pound  in  the  cylinder  can  very 
likely  be  cured  by  retarding  the  spark. 

To  sum  up,  then,  if  ignition  occurs  either  too  early  or  too  late  the 
engine  will  not  work  to  the  best  advantage  and  for  the  amount  of 
fuel  consumed  it  will  not  yield  the  maximum  amount  of  power. 

LESSON  IV. 

In  preceding  lessons  considerable  space  was  devoted  to  the  proper 
mixtures  of  fuel  and  air  necessary  to  obtain  the  best  results.  In  this 
connection  here  is  an  interesting  little  experiment  anyone  can  try 
with  the  ordinary  four-stroke  cycle  engine.  Start  the  engine  in  the 
usual  way  and  after  it  gets  to  running  nicely  close  the  fuel  valve  a 
little  at  a  time  quite  slowly  until  explosions  begin  to  occur  in  the 
muffler.  Now  throttle  the  air  supply  by  holding  a  piece  of  cardboard 
or  a  piece  of  board  on  the  end  of  the  air  pipe,  thus  reducing  the  air 
supply,  and  note  the  effect. 


14 


GASOLOGY. 


GAS  ENGINE  PRINCIPLES.  15 

The  explosions  will  cease  in  the  muffler  and  the  engine  will  work 
nicely  because  the  supply  of  air  has  been  cut  down  to  make  the  cor- 
rect mixture  with  the  fuel  admitted.  By  working  carefully  the  fuel 
valve  and  air  pipe  may  both  be  almost  closed  and  yet  the  explosions 
will  occur  regularly  and  be  all  right,  but  will  not  have  much  force 
because  only  a  small  amount  of  fuel  is  taken  into  the  cylinder  at 
each  charge. 

If,  when  the  amount  of  fuel  is  cut  down  so  low,  the  air  pipe  were 
left  with  the  full  opening,  the  mixture  would  be  so  lean  that  it  would 
not  ignite  at  all  and  the  engine  would  stop.  When  an  engine  runs 
on  a  weak  or  small  charge  as  just  explained  it  will -of  course  not  de- 
velop much  power.  This  little  experiment  not  only  illustrates  the 
effects  of  fuel  and  air  mixtures,  but  illustrates  also  a  means  for  gov- 
erning a  gas  engine  which  is  made  use  of  in  many  engines,  as  will  be 
more  fully  explained  in  a  subsequent  lesson. 

The  cylinder  of  a  gas  engine  is  made  of  a  close  grained  cast  iron 
and  when  well  designed  the  walls  are  of  practically  uniform  thick- 
ness throughout.  This  is  necessary  on  account  of  the  intense  heat, 
which  would  cause  unequal  expansion  and  dangerous  strains  if  the 
metal  varied  much  in  thickness.  The  cylinder  is  bored  as  smooth  as 
possible  and  in  the  best  constructions  it  is  ground  to  a  perfectly 
smooth  finish.  Some  manufacturers  claim  that  they  grind  the  cyl- 
inders slightly  tapering,  making  them  two  or  three  thousandths  of  an 
inch  smaller  at  the  head  end  than  at  the  crank  end.  Then  when  the 
engine  is  in  operation  the  greater  heat  at  the  head  end  causes  greater 
expansion  and  the  cylinder  sides  become  exactly  parallel.  Such  re- 
finements in  construction  are  practiced  only  on  the  higher  priced  ma- 
chines, such  as  automobile  engines  and  the  like.  Ordinary  gasoline 
engine  cylinders  are  merely  bored  out  as  true  as  possible  on  a  boring 
machine. 

It  has  been  proven  by  experiments  that  there  should  be  no  pockets 
or  chambers  on  the  side  of  the  combustion  chamber  in  which  a  part 
of  the  charge  may  accumulate.  It  appears  that  where  such  is  the 
case  that  the  gases  so  trapped  explode  a  little  later  than  the  main 
charge  and  are  liable  to  set  up  waves  of  pressure  in  time  or  synchro- 
nism with  the  waves  of  the  main  explosion.  These  two  waves  of 
force  occurring  at  the  same  time  and  meeting  are  apt  to  have  the 
effect  of  a  blow  on  the  inside  of  the  cylinder,  causing  an  abnormally 
high  pressure  for  an  instant  which  strains  the  entire  engine  without  in 
any  way  increasing  its  power. 

The  truth  of  this  assertion  has  been  proven  by  taking  indicator 
cards  from  an  engine  having  no  such  pockets,  then  screwing  a  short 
piece. of  pipe  capped  on  the  outer  end  into  the  combustion  chamber, 


16  GASOLOGY. 

and  taking  indicator  cards  again,  the  extremely  high  pressures 
were  clearly  shown  on  the  cards.  This  fact  would  seem  to  indicate 
that  the  inlet  and  exhaust  valves  should  both  open  directly  into  the 
clearance  space  of  the  cylinder,  or  if  they  open  into  a  chamber  on 
the  side  of  the  clearance  space,  ignition  should  take  place  in  the  valve 
chamber. 

Surrounding  the  cylinder^and  separated  from  it  by  a  short  space, 
the  exact  amount  depending  upon  the  size  of  the  cylinder,  there  is 
an  outside  casing  or  jacket.  This  casing  is  usually  made  of  cast  iron, 
although  in  some  instances  it  is  made  of  copper.  When  made  of  cast 
iron  it  may  be  entirely  separate  from  the  cylinder  or  it  may  be  cast 
with  the  cylinder  and  attached  thereto  at  intervals  in  the  process  of 
casting.  The  space  between  the  cylinder,  and  this  outer  casing  con- 
tains the  cooling  liquid,  which  may  be  either  water  or  oil.  Water  be- 
ing cheap  and  easy  to  obtain,  is  more  commonly  used  than  oil. 

Since  the  temperature  of  combustion  in  a  gas  engine  cylinder 
ranges  between  two  thousand  and  three  thousand  degrees,  and  since 
cast  iron  melts  at  a  temperature  of  about  two  thousand  three  hun- 
dred degrees  it  is  evident  that  some  means  must  be  provided  to  carry 
away  the  excess  heat.  This  is  accomplished  generally  by  means  of 
circulating  water  or  oil  around  the  cylinder.  Sometimes,  however, 
in  small  sized  engines  ribs  or  spines  of  metal  are  cast  on  the  outside 
of  the  cylinder,  thus  providing  a  large  radiating  surface  which  con- 
ducts the  heat  away  from  the  cylinder  to  the  air.  Such  engines  are 
known  as  air  cooled  engines.  This  method  works  very  satisfactorily 
with  engines  up  to  about  10-horse  power,  but  in  sizes  above  this  the 
heat  can  not  radiate  rapidly  enough  to  keep  the  cylinder  cool. 

Where  either  water  cooling  or  oil  cooling  is  resorted  to  there  are 
two  methods  of  circulating  the  liquid  around  the  cylinder,  either  the 
gravity  method  or  the  pump  method. 

In  the  first  case  advantage  is  taken  of  the  difference  in  weight 
between  equal  volumes  of  cold  water  and  hot  water,  or  of  cold  oil  and 
hot  oil  if  oil  is  the  liquid  used.  For  example,  at  a  temperature  of 
39  degrees  Fahrenheit  a  cubic  foot  of  water  weighs  sixty-two  and 
one-half  pounds,  while  at  212  degrees  Fahrenheit  a  cubic  foot  weighs 
only  fifty-nine  and  one-half  pounds.  The  hotter  the  water  the  less 
a  certain  volume  of  it  weighs.  If  we  have,  then,  a  gas  engine  cyl- 
inder connected  to  a  tank  as  shown  in  Fig.  5,  the  water  in  the  engine 
jacket  will  become  heated,  its  weight  will  be  less  than  an  equal  vol- 
ume in  the  tank  and  consequently  the  heavier  water  from  the  tank 
will  flow  in  by  gravity  through  pipe  B  and  push  the  lighter  water  out. 

Care  must  be  taken  to  see  that  an  air  vent  is  placed  in  the  highest 
point  of  pipe  A,  otherwise  a  bubble  of  air  or  steam  roay  form  at  that 


GAS  ENGINE  PRINCIPLES.  17 

point  and  prevent  circulation.  A  case  of  this  kind  recently  came  un- 
der the  writer's  notice.  The  vent  pipe  was  not  placed  in  the  highest 
part  of  the  pipe  and  the  cylinder  became  hot  enough  to  burn  the 
paint.  The  water  should  be  from  four  to  six  inches  higher  in  the 
tank  than  the  end  of  pipe  A  to  insure  circulation.  If  the  water  falls 
below  the  pipe  there  will  be  no  circulation. 

In  the  second  method  a  pump  is  used  to  force  the  water  from  the 
tank  through  the  cylinder.  A  small  rotary  pump  driven  by  the  engine 
shaft  is  generally  used.  This  method  insures  better  circulation.  In 
many  cases  the  water  is  delivered  from  the  discharge  pipe  in  the 
form  of  spray,  which  falls  thence  into  the  main  reservoir.  By  this 
method  radiation  of  the  heat  from  the  water  is  much  more  rapid  and 
a  smaller  quantity  of  water  is  required.  It  is  generally  conceded  that 
the  temperature  of  the  jacket  discharge  water  should  be  just  below  the 
boiling  point  or  in  the  neighborhood  of  180  degrees  in  order  to  obtain 
the  best  efficiency  from  the  engine.  If  the  jacket  water  is  very  much 
colder  the  gases  in  the  cylinder  lose  their  heat  and  consequently  their 
expansive  power  too  rapidly  and  the  engine  lacks  power. 

Oil  boils  at  a  higher  temperature  than  water  and  it  is  not  uncom- 
mon in  engines  cooled  with  oil  to  run  with  the  oil  in  the  jacket  much 
hotter  than  212  degrees.  If  the  engine  is  well  made  this  is  an  advan- 
tage rather  than  a  disadvantage  because  the  gases  do  not  lose  their 
heat  to  the  jacket  so  rapidly  and  a  larger  quantity  of  their  heat  is 
available  to  do  work  on  the  piston.  The  limit  of  heat  in  the  jacket  is 
reached  when  lubrication  of  the  piston  becomes  difficult  and  it  has 
a  tendency,  on  account  of  the  heat,  to  expand  and  stick  in  the  cyl- 
inder. 

LESSON  V. 

Another  method  of  cooling  which  has  been  proposed,  and  which 
is  used  in  an  auxiliary  way  to  some  extent,  is  to  introduce  water  di- 
rectly into  the  engine  cylinder.  This  may  be  accomplished  in  one  of 
two  ways ;  either  by  introducing  it  in  the  form  of  a  fine  mist  or  spray 
during  the  aspirating  stroke,  or  else  by  means  of  a  pump  during  the 
power  stroke. 

If  introduced  during  the  aspirating  stroke,  the  compression  of  the 
mixture  will  turn  the  water  into  steam  which  will  become  further  heat- 
ed after  ignition.  On  account  of  the  high  specific  heat  of  water,  it 
requires  a  large  quantity  of  heat  to  vaporize  it  or  to  raise  its  tempera- 
ture after  it  is  vaporized.  Since  this  heat  must  be  absorbed  from  the 
heat  of  combustion  of  the  charge  it  follows,  necessarily,  that  the  tem- 
perature of  the  mixture  in  the  cylinder  will  be  materially  reduced. 
If  very  much  water  is  introduced  it  may  absorb  so  much  of  the  heat 


18  GASOLOGY. 

generated  during  compression  that  the  gases  will  not  be  hot  enough 
to  ignite  readily.  Especially  will  this  be  true  if  the  charge  is  some- 
what lean.  This  accounts  for  the  fact  that  a  leak  of  water  from  the 
jacket  to  the  cylinder  makes  it  difficult  to  start  the  engine. 

Cooling,  in  the  method  just  described,  cannot  be  carried  out  com- 
pletely. Some  writers  declare  that  it  is  never  conducive  to  good  econ- 
omy in  any  case  because  it  reduces  the  temperatures  and  pressures  in 
the  cylinder.  The  results  of  tests  seem  to  prove,  however,  that  under 
certain  circumstances  it  may  be  advantageous  to  use.  In  kerosene 
engines  and  in  many  alcohol  engines  provision  is  made  to  use  a  water 
spray,  and  the  result  of  such  use  is  always  a  smoother  running  engine. 
A  heavily  loaded  kerosene  engine  will  pound  heavily  after  it  has  run 
for  some  time  unless  a  large  amount  of  jacket  water  or  else  a  spray 
of  water  is  used.  It  seems  advantageous  in  some  types  of  engines, 
both  from  an  economical  and  mechanical  viewpoint,  to  use  a  small 
amount  of  water  in  the  cylinder  in  addition  to  the  regulation  method 
of  cooling  by  means  of  jacket  water. 

Water  cooling  is  also  practiced  in  some  cases  as  respects  the 
products  of  combustion,  by  introducing  it  into  the  exhaust  pipe.  The 
effect  is  to  absorb  heat  from  the  gases  and  allow  them  to  escape  at  a 
lower  pressure,  thus  acting  to  some  extent  as  a  muffler.  This  practice 
does  not,  of  course,  affect  the  heat  in  the  cylinder  itself. 

In  very  large  engines  the  piston  must  be  cooled  as  well  as  the  cylin- 
der because  the  heat  in  the  central  part  of  a  large"  disc  of  iron,  which 
exposes  relatively  a  small  surface  to  the  cool  cylinder  walls,  can  not 
part  with  its  heat  rapidly  enough  to  keep  the  central  part  at  a  safe 
working  temperature.  Cooling,  in  such  cases,  is  accomplished  by 
circulating  water  under  pressure  within  the  hollow  part  of  the  piston, 
using  either  flexible  connections  or  telescoping  pipes  to  convey  the 
water. 

It  is  also  necessary  to  cool  the  exhaust  valve  by  a  water  jacket 
owing  to  the  high  degree  of  heat  of  the  exhaust  gases.  The  admis- 
sion valve  does  not  need  cooling  especially,  because  it  is  sufficiently 
cooled  by  the  fresh  charge  of  cold  gas  and  air,  although  it  is  cus- 
tomary to  bring  the  water  jacket  as  close  around  both  valves  as  can 
be  done  conveniently. 

The  volume  of  the  compression  space  is  an  important  consideration 
in  gas  engine  design  and  a  knowledge  of  the  part  it  performs  is  equal- 
ly of  value  to  the  man  who  operates  an  engine.  In  steam  engine  prac- 
tice it  is  a  well  recognized  fact  that  the  clearance  space  should  be 
small  in  order  to  insure  the  best  economy.  What  is  true  in  this  re- 
spect in  the  steam  engine  is  equally  true  in  the  gas  engine.  The 
highest  economy  demands  small  compression  volume.  There  is  a 


GAS  ENGINE  PRINCIPLES.  19 

practical  limit  beyond  which  high  compression  can  not  be  carried, 
and  this  limit  is  different  for  every  different  kind  of  fuel  used. 

In  a  previous  lesson  the  statement  was  made  that  there  is  an  exact 
relation  between  heat  and  work.  If  work  is  done  upon  a  gas  by  com- 
pressing it,  it  becomes  heated  and,  if  the  gas  afterwards  expands 
and  does  work  upon  the  piston  its  temperature  falls.  When  the 
charge  in  a  gas  engine  is  compressed  its  temperature  rises  in  propor- 
tion to  the  amount  it  is  compressed.  If  compression  is  carried  too 
high,  its  temperature  may  reach  the  point  at  which  it  will  ignite.  The 
vapor  of  gasoline  ignites  at  comparatively  low  temperatures,  and  it  has 
been  found  by  experience  that  if  it  is  compressed  much  above  eighty- 
five  pounds  per  square  inch  pre-ignition  will  take  place.  Alcohol 
vapor,  on  the  other  hand,  is  less  volatile  and  needs  a  higher  tempera- 
ture in  order  to  burn,  consequently  it  will  stand  a  higher  compression, 
and  with  higher  compression  it  yields  greater  power  for  a  given  quan- 
tity of  alcohol  consumed.  For  this  reason  alcohol  engines,  designed 
primarily  to  use  alcohol,  have  a  smaller  clearance  volume  than  do 
gasoline  engines.  Engines  designed  to  work  under  varying  condi- 
tions and  different  fuels  are  usually  given  a  clearance  volume  equal 
to  from  twenty  to  twenty-five  per  cent  of  the  volume  displaced  by  the 
piston.  There  are  certain  well-known  laws  which  govern  the  pres- 
sure, volume  and  temperature  of  gases,  which  will  presently  be  brief- 
ly alluded  to.  It  should  be  understood,  in  passing,  that  the  three 
quantities,  pressure,  volume  and  temperature,  are  inter-dependent, 
that  is,  when  one  changes,  the  other  two  also  change,  unless  some 
means  are  taken  to  maintain  one  of  them  constant.  The  principal 
law  connected  with  pressure  and  volume  is  known  as  "Boyle's  Law." 
It  may  be  stated  thus:  The  pressure  of  a  gas  varies  inversely  as 
the  volume,  if  the  temperature  is  kept  constant,  or  the  volume  varies 
inversely  as  the  pressure  with  the  temperature  constant.  Stated  in 
plainer  words,  it  means  that  if  a  given  volume  of  gas  is  compressed 
to  one-half  its  volume,  the  pressure  will  be  doubled.  For  example,  if 
a  cylinder  full  of  air  or  any  other  gas  at  the  pressure  of  the  atmos- 
phere be  compressed  to  half  a  cylinder  full,  the  pressure  will  be 
doubled,  provided  some  means  is  provided  to  keep  the  temperature  of 
the  gas  from  rising.  In  other  words,  if  air  at  14.7  pounds  pressure 
is  reduced  to  half  that  volume  its  pressure  will  be  29.4  pounds  ab- 
solute pressure  or  14.7  pounds,  as  shown  on  a  steam  gauge. 

The  law  relating  to  temperature  and  pressure  states  that  the  pressure 
varies  directly  as  the  absolute  temperature,  provided  the  volume  is 
kept  constant,  or  the  volume  varies  directly  as  the  absolute  tempera- 
ture, provided  the  pressure  is  kept  constant.  This  means  that  if  a  cyl- 
inder full  of  gas  be  heated  the  pressure  will  rise  in  direct  proportion  to 


20  GASOLOGY. 

the  absolute  temperature.  Consequently,  if  we  simply  took  the  cyl- 
inder full  of  gas  and  heated  it,  or  if  it  was  an  imnammable  gas,  if  we 
burned  it,  the  increase  in  heat  would  cause  the  pressure  to  increase  in 
exact  proportion  to  the  increase  in  temperature. 

It  is  upon  these  two  laws  that  all  theoretical  calculations  in  re- 
gard to  gas  engines  are  worked  out.  Furthermore,  it  is  upon  just  such 
considerations  as  these  that  the  size  of  the  clearance  space  is  calculated 
in  order  to  give  any  compression  pressure  which  we  may  desire. 

An  example  of  heating  due  to  compression  is  often  witnessed  in  the 
case  of  starting  a  gas  engine  in  cold  weather.  It  may  be  too  cold  to 
start  the  first  few  times  the  engine  is  turned  over,  but  if  it  is  turned 
rapidly  a  few  times  the  cylinder  may  be  sufficiently  warmed  by  the 
compression  of  the  gas  to  cause  the  gasoline  to  vaporize. 


CHAPTER  II 


IGNITION,  PRIMARY  BATTERIES 

LESSON  VI. 

There  are  three  methods  in  common  use  for  igniting  the  charge 
in  gas  engines.  They  are  by  means  of  a  hot  tube  or  torch,  by  compres- 
sion, and  by  electricity.  The  hot  tube  is  one  of  the  oldest  methods,  but 
has  fallen  largely  into  disuse  except  as  an  emergency  device.  It 
finds  its  widest  application,  at  the  present  time,  as  an  auxiliary  de- 
vice to  be  used  in  case  something  goes  wrong  with  the  electric  igniter. 
Igniting  by  compression  is  used  only  on  a  few  types  of  engines,  such 
as  the  Hornsby-Akroyd,  Diesel,  and  a  few  others.  Electric  ignition  in 
one  form  or  another  is  the  method  almost  universally  adopted.  It  is 
the  easiest  to  handle,  the  most  reliable  and  certain  in  action,  and 
provides  for  the  closest  regulation  of  the  time  of  ignition,  which,  by 
the  way,  is  a  very  important  item  in  the  economical  operation  of  a 
gas  engine. 

Let  us  first  consider  the  hot  tube  system  of  ignition.  This  can  be 
best  explained  with  reference  to  the  accompanying  diagram,  Fig.  6. 
A  small  tube,  T ,  closed  at  the  outer  end,  is  screwed  into  the  com- 
pression chamber  of 
the  engine.  Just 
below  this  tube  there 
is  a  gas  jet  in  the 
form  of  a  Bunsen 
burner  which  is  sup- 
plied with  gasoline 
by  a  pipe  which 
leads  from  a  reser- 
voir on  the  top  of 
the  engine.  Sur- 
rounding both  the 
burner  and  the  tube 
there  is  a  cast  iron 
box  with  a  chimney 
on  the  top.  This  box 
prevents  air  currents  from  striking  the  flame  and  at  the  same  time 
directs  the  flame  upon  the  tube  at  the  desired  point.  The  chimney 
is  lined  with  asbestos  to  prevent  radiation  of  the  heat  generated  by 
the  flame. 


FIG.  6. 


22  GASOLOGY. 

In  operation,  the  action  of  the  hot  tube  is  as  follows :  A  few  min- 
utes before  starting  the  engine  the  burner  is  lighted  and  the  tube  is 
brought  up  to  a  red  heat,  then  when  the  charge  is  compressed  a  part 
of  the  inflammable  gas  enters  the  tube  and  when  it  reaches  the  red 
portion  it  becomes  ignited.  On  the  exhaust  stroke  there  will  be 
some  burnt  gases  still  left  in  the  tube  when  the  new  charge  enters 
the  cylinder.  When  this  charge  is  compressed,  the  burnt  gases  re- 
maining in  the  tube  from  the  previous  charge  must  be  compressed 
until  the  new  charge  meets  the  hot  portion  of  the  tube  before  ig- 
nition can  again  take  place.  Consequently,  if  the  burner  heats  the 
tube  near  where  it  enters  the  cylinder,  ignition  must  occur  earlier 
than  if  the  hot  portion  is  further  out  toward  the  end  of  the  tube. 
In  some  engines  the  position  of  the  burner  is  made  adjustable  in  order 
to  vary  the  time  of  ignition,  in  others  the  burner  is  fixed  in  position  at 
a  point  where  it  has  been  found  by  experience  to  give  the  best  re- 
sults. 

The  life  of  an  ordinary  iron  tube  is  very  short,  being  only  a  few 
days  at  most.  Nickel,  steel  or  porcelain  tubes  last  much  longer, 
but  are  more  expensive.  The  uncertainty  as  to  timing  of  ignition,  the 
bother  of  starting  and  the  delay  caused  by  the  burning  out  of  the 
tubes  makes  this  form  of  ignition  anything  but  efficient. 

Prof.  Hutton  in  his  book,  "The  Gas  Engine,"  has  the  following  to 
say  about  hot  tube  ignition: 

The  time  of  ignition  with  the  hot  tube  will  depend  upon: 

1.  The  length  of  the  tube. 

2.  The  size  or  volume  of  the  passage  leading  to  the  tube. 

3.  The  amount  or  degree  of  compression  of  the  mixture  by  the 
piston. 

4.  The  temperature  of  the  tube;  the  hotter  the  tube,  the  earlier 
the  ignition;  the  cooler  the  tube,  the  later. 

5.  The  fact  whether  it  was  hottest  near  the  open  or  the  closed 
end;  if  heated  near  the  open  end,  the  earlier  the  ignition. 

6.  The  temperature  of  the  mixing  and  igniting  chambers. 

7.  The  temperature  of  the  jacket- water  outlet. 

8.  The  speed  of  the  engine. 

9.  The  quality  or  proportions  of  the  air  and  fuel  admitted. 

10.  The  pressure  of  the  intake  or  suction  stroke. 

11.  The  governing  action  and  the  system  of  governing. 

12.  Leakage;  at  piston,  at  exhaust,  past  valves. 

13.  The  state  of  the  surfaces  of  the  tube,  outside  and  in. 

14.  The  location  of  the  tube  with  respect  to  receiving  and  acting 
on  new  or  fresh  mixtures  or  mixtures  containing  burnt  gases. 


,  PRIMARY  BATTERIES. 


Ignition  by  Compression. — In  the  Diesel  engine  a  charge  of  air 
is  drawn  into  the  cylinder  on  the  aspirating  or  charging  stroke — 
but  no  fuel.  This  air  is  compressed  to  a  very  high  pressure,  usually 
above  five  hundred  pounds  per  square  inch.  When  air  is  compressed 
so  strongly  the  work  done  upon  it  is  transformed  into  heat  and  its 
temperature  rises  very  high.  If  now,  when  the  piston  reaches  the 
end  of  its  stroke,  a  jet  of  oil  is  pumped  in,  this  oil  will  be  ignited 
by  the  hot  air  and  no  other  form  of  igniter  will  be  needed.  A  gov- 
ernor attached  to  the  pump  regulates  the  time  during  the  power 
stroke  that  the  oil  jet  is  admitted,  which  generally  does  not  exceed 
one-tenth  of  the  stroke. 

Fig.  7  shows  the  method  of  igniting  the  charge  in  the  Hornsby- 
Akroyd  oil  engine.  The  chamber  at  the  left  of  the  cylinder  is  not 
water  jacketed.  It  is  first  heated  by  an  auxiliary  burner  to  a  red 
heat.  Then  when 
the  piston  makes  its 
first  outward  stroke 
air  is  drawn  into  the 
cylinder  and  a  thin 
jet  of  kerosene  is 
forced  into  the  hot 
chamber  and  is  in- 
stantly vaporized. 
On  the  compression 
stroke  the  air  is 
forced  back  through 
the  narrow  neck  into 
the  vaporizing  chamber  where  it  mixes  with  the  fuel.  Ignition  is 
caused  by  the  heating  effects  of  compression,  friction,  and  the  heat  of 
the  vaporizer.  At  first  thought  it  might  be  supposed  that  when  the 
oil  first  enters  the  vaporizer  it  would  be  ignited,  but  this  can  not 
occur  because  it  has  no  air  to  combine  with.  The  air  that  is  entering 
the  cylinder  during  the  charging  stroke  is  moving  toward  the  rear 
of  the  cylinder,  away  from  the  fuel.  On  the  compression  stroke  this 
air  is  forced  into  the  chamber  with  the  fuel  and  when  the  compression 
stroke  is  nearly  completed  the  air  has  mixed  with  the  vaporized  fuel 
sufficiently  to  cause  an  explosive  mixture  and  ignition  takes  place.  A 
governor  controls  the  stroke  of  the  pump  and  allows  the  correct 
amount  of  oil  to  be  delivered  to  maintain  the  speed  of  the  engine. 
There  are  no  means  for  changing  the  time  of  ignition.  This  engine 
is  adapted  for  using  kerosene  or  heavier  oils. 

Electric  ignition,  as  before  stated,  is  used  by  nearly  all  makers 
of  gas  engines  at  the  present  time.  There  are  many  different  systems 
in  use,  some  of  which  differ  from  each  other  in  essential  particulars 


24 

and  some  only  in  minor  details.  A  complete  knowledge  of  electrical 
ignition  must  necessarily  include  a  considerable  knowledge  of  elec- 
tricity and  much  more  than  can  be  presented  in  this  series  of  lessons. 
However,  in  order  to  make  the  subject  as  plain  as  possible  it  will  first 
be  necessary  to  consider  some  of  the  fundamental  principles  of  elec- 
tricity and  that  we  will  now  proceed  to  do. 

To  begin  with,  electricity  is  one  form  of  energy,  just  as  heat  or 
motion  is  a  form  of  energy.  Electricity  must  always  be  generated 
by  some  outside  source  of  power  and  a  given  amount  of  power  is 
always  consumed  in  generating  a  certain  amount  of  electricity.  We 
know  some  things  electricity  can  do;  we  know  some  of  the  laws  govern- 
ing its  action,  and  we  know  something  about  how  to  handle  it ;  but  we 
do  not  know  just  exactly  what  electricity  is.  This  need  not  trouble 
us,  however,  because  we,  as  gas  engineers,  are  concerned  with  the 
practical  application  of  electricity  rather  than  with  its  theory. 

Electricity  may  be  generated  with  a  machine  as  in  a  dynamo,  or 
chemically,  as  in  a  cell;  the  character  and  properties  of  the  current 
delivered  are  the  same  in  either  case. 

The  unit  for  measuring  the  intensity  of  an  electric  current  is  called 
a  volt.  It  is  the  measure  of  electrical  pressure  or  electro-motive  force 
just  as  pounds  on  a  steam  gauge  represent  steam  pressure,  or  water 
pressure  if  the  gauge  is  attached  to  a  water  pipe.  The  unit  for  meas- 
uring the  amount  of  current  is  called  an  ampere.  This  may  be  rep- 
resented by  gallons  in  the  case  of  water.  The  flow  of  electricity  can 
be  represented  very  easily  by  comparing  it  with  the  flow  of  water. 
For  example,  we  may  have  a  low  voltage  and  a  large  current  and  con- 
sequently a  large  amount  of  electricity  delivered.  In  the  same  way  we 
may  have  a  small  pressure  and  a  large  stream  of  water  and  in  a  given 
time  a  large  volume  of  water  will  be  delivered.  Or  we  may  have  high 
voltage  and  small  amperage  and  a  large  amount  of  electricity  de- 
livered just  as  a  high  pressure  of  water  and  a  small  sized  stream  will 
deliver  a  large  volume  of  water. 

Voltage  applies  only  to  the  pressure  of  electricity  and  amperes  to 
the  size  of  the  current.  We  may  have  a  very  high  voltage  and  small 
current  or  low  voltage  and  large  current.  These  terms  will  be  used 
again  and  again  in  these  lessons  and  the  student  should  try  to  re- 
member just  what  they  mean. 

LESSON  VII. 

Batteries  are  of  two  principal  kinds,  primary  batteries  and  sec- 
ondary batteries.  A  primary  battery  generates  electrical  current  by 
means  of  chemical  action.  A  secondary  battery  must  first  be 


IGNITION,  PRIMARY  BATTERIES 


25 


charged  by  means  of  some  outside  source  of  current.  This  current 
sets  up  chemical  action  within  the  cells  of  the  battery  which  changes 
the  chemical  nature  of  some  of  the  elements  in  such  a  way  that  when 
the  battery  is  connected  up  to  do  work,  these  elements  revert  to  their 
original  form  and  electrical  current  is  generated.  Ordinary  batteries, 
either  of  the  wet  cell  or  the  dry  cell  variety,  such  as  are  used  gen- 
erally for  the  electrical  ignition  of  gas  engines,  are  familiar  ex- 
amples of  primary  batteries.  Storage  batteries  are  examples  of  sec- 
ondary batteries. 

Primary  batteries  are  made  up  of  a  number  of  simple  voltaic  or 
galvanic  cells  which  are  connected  together  by  means  of  wires.  In 
order  to  understand  the  working  of  a  battery,  we  must  first  study 
the  construction  of  a  cell  and  the  action  which  takes  place  between  its 
parts.  Figure  8  is  an  illustration  of  a  very  simple  form  of  cell.  It 
consists  of  a  jar  nearly  filled  with  weak  suphuric  acid,  called  the 
electrolyte,  in  which  there  is 
suspended  a  plate  of  copper 
and  a  plate  of  zinc.  These 
are  marked  C  and  Z,  respec- 
tively, in  the  figure.  The 
zinc  plate  is  the  positive 
element  in  any  cell  and  the 
other  plate  the  negative  ele- 
ment. Curiously  enough, 
however,  the  binding  post  at- 
tached to  the  zinc  element  is 
known  as  the  negative  pole 
and  the  other  as  the  posi- 
tive pole  of  the  cell.  If  the 
two  poles  be  connected  by 
means  of  wires  an  electrical 
current  will  flow,  in  the  di- 
rection shown  by  the  arrows, 
from  the  copper  plate 
through  the  connectors  to  the 
zinc  plate.  In  some  types  of 
cells  there  is  very  little  local 


FIG.  8. 


action  unless  the  cell  is  working  on  a  closed  circuit,  bu>t  in  this  type 
of  cell  the  zinc  is  attacked  by  the  electrolyte  whether-  it  is  on  open 
or  closed  circuit,  although  the  action  is  not  so  strong  when  the  cir- 
cuit is  open  as  it  is  when  it  is  closed.  When  the  two  wires  a  and  b 
are  touched  together,  chemical  action  it  set  up  strongly 


26  GASOLOGY. 

cell.  A  part  of  the  acid  of  the  electrolyte  is  constantly  decompos- 
ing and  uniting  with  the  zinc,  forming  a  new  substance,  zinc  sul- 
phate, and  at  the  same  time  an  electric  current  is  generated  by  this 
chemical  action. 

The  amount  of  current  which  is  generated  is  proportional  to  the 
amount  of  zinc  consumed  or  changed  into  zinc  sulphate.  There  is 
a  similarity  between  an  electrical  cell  and  a  furnace.  In  the  latter, 
coal  is  burned  and  heat  is  generated;  in  the  former,  zinc  is  con- 
sumed and  electricity  is  generated.  The  amount  of  heat  that  is 
generated  depends  upon  the  amount  of  fuel  burned,  and,  in  like 
manner,  the  amount  of  electricity  that  is  generated  depends  upon  the 
quantity  of  zinc  consumed.  Both  the  generation  of  heat  and  of 
electricity  are  examples  of  chemical  activity. 

Polarization. — When  the  sulphur  and  oxygen  of  the  electrolyte 
unite  with  the  zinc,  forming  zinc  sulphate,  hydrogen  gas  is  set  free, 
which  appears  as  small  bubbles  on  the  copper  plate,  unless  there  is 
some  other  substance  at  that  point  for  the  hydrogen  to  unite  with. 
The  formation  of  the  bubbles  of  hydrogen  gas  represents  lost  energy 
unless  they  can  combine  with  some  other  substance,  in  which  event 
the  energy  used  in  their  formation  is  given  back  and  adds  to  the 
electro  motive  force  of  the  cell.  Their  presence  on  the  copper  plate 
adds  to  the  internal  resistance  of  the  cell  very  greatly  and  reduces 
the  amount  of  current  which  the  voltage  of  the  cell  can  send  through 
any  external  circuit.  The  formation  of  bubbles  of  hydrogen  gas  on 
the  copper  plate  is  called  polarization  and  the  removal  of  them  by  any 
means  is  called  depolarization.  All  cells  in  commercial  use  are 
designed  to  prevent  polarization  as  far  as  possible,  and  generally 
by  chemical  means.  In  this  way,  not  only  is  the  internal  resistance 
of  the  cell  prevented  from  increasing,  but  the  electro-motive  force 
of  the  cell  is  actually  increased. 

The  Edison- Lalande  cell  is  an  example  of  one  of  the  best  and  most 
popular  cells  used  for  gas  engine  ignition.  S,ince  it  is  a  very  effi- 
cient type  of  cell,  and  is  arranged  to  prevent  polarization,  it  will 
repay  a  little  study.  The  electrolyte  is  either  a  solution  of  potassium 
hydrate  (caustic  potash)  or  sodium  hydrate  (caustic  soda),  and 
water.  Zinc  forms  one  of  the  elements  and  the  other  is  formed  by 
mixing  together  cupric  oxide  and  magnesium  chloride  and  forcing 
the  mixture  into  a  suitably  prepared  plate  under  pressure.  This 
plate  is  then  heated  and  the  mass  becomes  thoroughly  bound  together. 
This  composition  plate  is  suspended  by  means  of  copper  channel 
strips,  in  the  electrolyte,  between  two  plates  of  zinc.  The  terminals 
of  the  elements  pass  up  through  a  cover  plate  which  insulates  them 


IG>*/TION,  PRIMARY  BATTERIES.  27 

from  each  other.  So  long  as  there  is  no  metallic  connection  between 
the  two  terminals,  that  is,  between  the  zinc  plate  and  the  composition 
plate,  there  is  practically  no  action  in  the  cell.  In  other  words,  the 
zinc  is  not  attacked  unless  the  circuit  is  closed.  In  this  respect 
it  differs  from  the  first  cell  described. 

The  internal  action  of  this  cell  is  as  follows:  When  the  external 
circuit  is  closed,  some  of  the  solution  of  potassium  hydrate  in  con- 
tact with  the  zinc  plates  decomposes  and  part  of  it  unites  with  the 
zinc,  forming  a  new  chemical  substance,  while  the  hydrogen  goes 
over  to  the  cupric  oxide  plate  and  there  unites  with  the  oxygen 
of  the  plate,  thus  forming  water  and  setting  free  metallic  copper. 
The  cupric  oxide  is  the  depolarizer  since  the  oxygen  it  contains  is 
always  ready  and  at  hand  to  combine  with  the  bubbles  of  hydrogen 
gas.  This  cell,  when  in  use,  will  give  an  electro-motive  force  of 
about  .7  volt.  'When  freshly  charged  it  will  give  a  slightly  higher 
voltage.  The  internal  resistance  is  very  low  and  it  gives  a  good 
strong  current.  Since  the  caustic  potash  will  absorb  carbon  dioxide 
gas  from  the  air  and  thus  lose  its  virtue  as  an  electrolyte,  it  is  nec- 
essary to  cover  the  liquid  in  the  cell  with  a  heavy  mineral  oil. 

These  cells  do  not  need  any  attention  until  they  are  exhausted, 
that  is,  until  either  the  zinc  is  consumed,  the  composition  plate  is 
red  all  through  (which  can  be  told  by  digging  into  it  with  a  pen 
knife),  or  the  electrolyte  is  too  weak.  It  is  not  much  trouble  to  re- 
charge them.  If  the  elements  are  all  right,  that  is,  not  complete- 
ly worn  out,  all  that  is  necessary  to  do  is  to  pour  out  the  old  electrolyte 
and  make  a  new  one  by  using  caustic  potash  and  water.  Care  must 
be  taken  that  the  top  of  the  copper  oxide  plate  is  at  least  an  inch 
below  the  top  of  the  liquid,  otherwise  the  cell  will  be  almost  sure 
to  fail. 

Arrangement  of  Cells. — The  usual  way  to  arrange  a  number  of 
cells,  to  form  a  battery  for  ignition  purposes,  is  what  is  called  a  se- 
ries, that  is,  the  zinc  from  one  cell  is  connected  to  the  carbon  of 
the  next  one  and  so  on.  One  cell  is  arranged  directly  behind  the 
other  in  this  arrangement  and  the  current  is  compelled  to  pass 
through  all  of  the  cells. 

Another  method  of  arranging  cells  in  a  battery  is  to  connect  all 
of  the  zincs  together  and  all  of  the  carbons  together.  This  amounts 
to  the  same  thing  as  making  one  large  cell  having  a  zinc  as  large 
as  the  sum  of  all  the  zincs  and  a  carbon  plate  whose  area  is  equal 
to  the  sum  of  all  the  carbons.  This  method  of  connecting  is  called 
connecting  in  parallel.  For  some  kinds  of  work  the  series  method  of 
connecting  is  preferable,  while  for  other  kinds  of  work  better  re- 


28  GASOLOGY. 

suits  are  obtained  when  the  cells  are  arranged  in  parallel.  A  dis- 
cussion of  this  phase  of  the  question  will  be  left  for  some  subse- 
quent lesson. 

LESSON  VIII. 

Dry  cells  are  made  up  in  practically  the  same  way  as  wet  cells  and 
with  the  same  active  materials.  The  elements  are  zinc  and  carbon. 
The  outer  portion  or  can  is  made  of  zinc  and  surrounds  a  rod  of  car- 
bon which  does  not  quite  reach  the  bottom  of  the  can.  The  electrolyte 
consists  generally  of  a  solution  of  sal-ammoniac  and  water  mixed 
with  zinc  chloride.  This  occupies  the  space  next  to  the  zinc  and  is 
held  in  position  by  some  absorbent  material,  like  blotting  paper, 
which  is  completely  saturated  by  the  solution.  The  space  between 
the  electrolyte  and  the  carbon  rod  is  filled  with  some  substance  such 
as  powdered  carbon  and  manganese  dioxide  which  acts  as  a  depolar- 
izer. The  details  of  construction  and  the  ingredients  which  are  used 
are  not  the  same  in  all  dry  cells,  but  the  description  just  given  will 
give  the  reader  a  good  general  idea  of  how  they  are  constructed.  The 
tops  of  dry  cells  are  covered  with  hard  pitch,  which  prevents  the 
evaporation  of  the  electrolyte,  while  the  outside  of  the  can  is  insu- 
lated with  paper. 

The  chemical  action  that  takes  place  in  a  dry  cell  is  the  same 
as  that  which  occurs  in  a  wet  cell,  having  the  same  elements  and  the 
same  electrolyte,  but  owing  to  the  fact  that  this  action  takes  place 
in  a  paste  instead  of  in  a  liquid  it  is  not  nearly  so  rapid.  A  good 
dry  cell  when  new  will  show  on  dead  short  circuit — that  is  right 
across  the  terminal — about  one  and  one-half  volts,  sometimes  a 
little  more,  and  a  current  strength  of  from  twenty  to  thirty  am- 
peres. When  a  dry  cell  battery  has  been  in  use  for  a  number  of 
hours  both  the  voltage  and  amperage  will  decrease — the  battery  get 
weaker;  but  if  it  is  allowed  to  stand  idle  for  some  time  it  will  re- 
cover its  normal  strength.  Sometimes  when  a  dry  battery  is  nearly 
run  down  it  has  sufficient  strength  to  give  a  spark  that  will  ignite 
every  charge  for  a  few  minutes  and  then  it  will  gradually  die  down 
and  the  engine  will  stop.  It  often  happens  that  only  one  or  two 
cells  of  a  battery  are  worn  out,  while  the  others  are  still  in  good 
condition.  If  these  poor  cells  are  taken  out  and  new  ones  substi- 
tuted the  battery  will  be  in  good  condition  again.  It  will  pay  any 
one  who  uses  dry  batteries  to  have  an  ammeter  and  test  the  cells, 
each  one  separately,  whenever  he  suspects  that  they  are  not  right.  A 
good  enough  ammeter  can  be  purchased  for  three  or  four  dollars 
and  directions  for  using  come  with  the  instrument.  Any  cell  that 


IGNITION,  PRIMARY  BATTERIES  29 

shows  less  than  six  amperes  is  worthless  and  should  be  thrown  away. 
It  is  a  good  plan  to  test  new  cells  at  the  time  of  purchasing.  The 
writer  only  last  winter  got  hold  of  a  new  battery  that,  presumably  at 
least,  had  never  been  used  and  yet  it  was  worthless.  It  was  probably 
old  and  the  electrolyte  had  slowly  evaporated.  It  is  said  that  a  cell 
will  not  last  much  over  three  years  even  if  not  used  at  all,  due  to 
slow  evaporation  of  the  moisture  that  it  contains.  Such  a  cell  could 
be  made  good  again  by  introducing  some  new  electrolyte  through  a 
hole  in  the  top  or  sides.  Ordinarily,  however,  when  a  dry  cell  gives 
out  it  can  not  be  revived  and  the  only  thing  to  do  is  to  throw  it  away 
and  get  a  new  one. 

For  ordinary  ignition  purposes  a  battery  made  up  of  from  four  to 
six  cells  is  sufficient.  A  larger  number  of  cells  will  give  a  hotter 
name,  but  the  action  is  so  intense  that  it  will  injure  the  contact 
points  of  the  igniter,  causing  them  to  wear  rapidly  and  become  pitted. 
Large  sized  cells  are  more  economical  than  the  smaller  sizes  even 
if  they  do  cost  more  than  twice  as  much,  but  they  will  last  consid- 
erably more  than  twice  as  long.  Of  course,  if  they  are  accidentally 
short  circuited  they  will  be  ruined  just  as  quickly  and  the  loss  is 
greater.  It  does  not  take  very  long  for  a  dry  battery  to  become 
ruined  by  short  circuiting  either ;  ten  or  fifteen  minutes  will  ruin  any 
battery  absolutely. 

Care  should  be  taken  in  connecting  up  any  battery,  either  of  wet 
or  dry  cells,  to  see  that  a  good  grade  of  insulated  wire  is  used,  pref- 
erably rubber  covered  wire,  and  that  the  ends  of  the  wire  that  are 
attached  to  the  binding  posts  of  the  cells  are  scraped  clean  and 
bright.  A  film  of  copper  oxide  sometimes  gathers  on  copper  wire  that 
offers  a  great  deal  of  resistance  to  the  passage  of  a  current  of  elec- 
tricity and  consequently  it  is  necessary  to  scrape  the  surfaces  that 
form  contact  perfectly  clean.  Electricians  in  putting  up  elec- 
trical wiring  usually  solder  the  joints  together  to  insure  good  con- 
tact and  to  make  certain  that  no  oxide  can  form  between  the  parts 
in  contact  and  prevent  the  free  flow  of  the  current.  The  nuts  on 
the  binding  posts  should  be  screwed  down  tightly.  A  loose  con- 
nection will  soon  become  oxidized  and  prevent  electricity  from  flow- 
ing. In  fact,  a  loose  connection  either  in  the  battery  or  on  the  en- 
gine is  very  frequently  the  cause  of  an  engine's  refusing  to  run. 

Batteries  should  be  kept  in  a  clean,  dry  place  and  the  battery 
box  should  be  kept  covered  to  prevent  any  pieces  of  metal  or  tools 
from  accidentally  finding  their  way  into  the  box  and  short  circuiting 
some  of  the  cells. 


30  GASOLOGY. 

Wet  cells  can  be  recharged  by  putting  in  a  new  solution  and  new 
elements.  If  the  elements  are  carbon  and  zinc,  the  zinc  is  all  that 
needs  renewing.  The  carbon  does  not  wear  out.  The  zinc  plate  is 
all  right,  even  if  quite  thin,  until  it  begins  to  fall  apart.  When 
new  zincs  are  needed  it  pays  to  make  a  new  solution.  In  the  case 
of  the  Edison-Lalande  cell,  both  the  zinc  and  copper  oxide  plate  will 
become  worn  out  and  both,  together  with  the  solution,  will  need  re- 
newing. Directions  are  usually  sent  out  with  the  batteries  for  re- 
charging and  if  these  are  followed  faithfully  there  will  be  no  trouble. 
The  chemicals  used  in  recharging  cells  are  inexpensive  and  the  cost 
of  renewal  is  not  very  great.  The  largest  cost  is  for  zincs  and  cop- 
per oxide  plates. 

All  zincs  used  in  electrical  cells  are  amalgamated.  This  is  done 
by  first  cleaning  the  zinc  plate  thoroughly  and  then  rubbing  a  little 
mercury  over  it.  The  mercury  unites  with  the  zinc  and  protects  it 
from  local  electrical  action,  and  not  only  makes  the  cell  give  greater 
current,  but  prevents  the  zinc  from  wearing  away  so  rapidly.  Com- 
mercial zinc  is  always  impure.  It  contains  particles  of  iron  and 
other  impurities,  which  would  cause  electrical  action  on  the  neighbor- 
ing particles  of  zinc.  This  is  prevented  by  the  coating  of  mercury 
and  so  causes  the  zinc  to  last  longer  and  also  give  better  service. 
Curiously  enough,  as  the  zinc  is  gradually  taken  into  solution  by  the 
electrolyte  and  the  plate  becomes  thinner,  the  mercury  is  not  affected 
but  retains  its  place  on  the  surface  of  the  plate  to  the  very  last. 


CHAPTER  III 

MAGNETISM  AND  COILS 


LESSON  IX. 

On  the  shores  of  Lake  Superior  and  in  various  other  parts  of  the 
world",  there  is  found  a  peculiar  ore  which  will  attract  iron.  The 
ore  was  first  found  by  the  ancients  in  the  city  of  Magnesia  in  Asia 
Minor  and  they  called  its  property  of  attracting  iron  magnetism. 
The  ore  is  an  iron  ore  somewhat  similar  to  the  scale  that  falls  from 
red  hot  iron  on  a  blacksmith's  anvil  and  is  called  magnetite.  Pieces 
of  this  ore,  when  suspended,  will  always  point  toward  the  north. 
It  was  in  early  times  used  in  navigation  for  a  compass,  and  was 
hence  called  a  leading  stone  or  lodestone.  It  was  subsequently  dis- 
covered that  if  a  piece  of  hardened  steel  be  rubbed  on  a  piece  of  lode- 
stone  it  also  be- 
came magnetic,  and 
thus  the  compass 
needle  was  discov- 
ered. The  former 
is  a  natural  magnet, 
the  latter  artificial. 

Artificial  magnets 
when  of  hard  steel 
retain  their  mag- 
netism a  long  time 
and  are  called  per- 
manent magnets.  If 
of  soft  iron  or  soft 
steel,  they  lose  their 
magnetism  quickly, 
almost  instantly,  in 


FIG.  9. 


fact.     The  ordinary 

form   of  permanent 

magnet  is  a  horseshoe  shape,  having  a  soft  bar  or  keeper  called  an 

armature  across  the  ends  to  prevent  loss  of  magnetism. 

Lines  of  Force. — If  a  straight  bar  of  hard  steel  which  has  first 
been  magnetized  be  placed  in  iron  filings,  the  filings  will  adhere  in 
tufts  to  each  end,  but  not  in  the  middle  of  the  bar.  The  two  ends 


32  GASOLOGY. 

of  the  bar  are  called  the  poles,  one  the  north  pole,  the  other  the 
south  pole.  The  north  pole  of  a  bar  magnet  will  attract  the  south  pole 
of  a  compass  needle  and  repel  the  north  pole.  Unlike  poles  of  mag- 
nets attract  each  other  and  like  poles  repel.  Since  the  earth  is  a  great 
magnet  whose  poles  very  nearly  coincide  with  the  geographical  poles, 
they  attract  the  magnetic  needle.  If  iron  filings  be  placed  on  a  smooth 
piece  of  paper  that  is  held  above  the  poles  of  a  magnet,  and  the 
paper  is  shaken  to  agitate  the  filings,  they  will  arrange  themselves 
as  shown  in  Fig.  9;  and  if  the  paper  is  held  over  only  one  pole  the 
filings  will  arrange  themselves  in  radial  lines.  The  lines  along 
which  the  filings  arrange  themselves  are  called  lines  of  magnetic 
force.  The  actual  lines  of  force  are,  of  course,  invisible,  but  their 
direction  and  existence  are  shown  by  the  filings.  The  direction  of 
these  lines  is  assumed  to  be  from  the  north  pole  to  the  south  pole 
through  the  air  or  surrounding  medium. 

If  a  piece  of  wire  be  wound  into  a  long  spiral  and  a  current  of 
electricity  be  sent  through  it,  it  will  have  all  of  the  properties  of 
a  magnet,  with  a  north  pole  and  a  south  pole  and  a  neutral  region 
between.  If  suspended,  it  will  assume  a  north  and  south  direction. 
If  the  coil  be  made  of  insulated  wire  and  wound  around  a  soft  iron 
rod,  the  latter  will  become  what  is  called  an  electromagnet,  with  all 
the  properties  of  a  bar  magnet.  When  the  current  of  electricity  is 
shut  off,  however,  it  quickly  loses  its  magnetism,  all  except  a  very 
small  amount  called  residual  magnetism. 

Electro  Magnetic  Induction. — This  can  be  shown  experimentally 
by  constructing  two  coils  of  wire  wound  over  paper  or  wooden  tubes, 
using  insulated  wire.  One  tube  should  be  small  enough  to  slip 
easily  inside  of  the  other  after  the  winding  is  done.  The  ends  of  the 
larger  coil  should  be  wound  several  times  around  a  compass  and  then 
fastened  together.  The  two  ends  of  wire  of  the  smaller  coil  should 
be  attached  to  the  binding  posts  of  a  galvanic  cell.  If,  now,  the 
small  coil  be  inserted  in  the  larger  one,  the  compass  needle  will  be 
deflected  and  the  same  thing  will  happen  if  it  is  withdrawn.  This 
shows  that  a  current  of  electricity  flows  through  the  larger  coil,  oth- 
erwise the  compass  needle  would  not  be  disturbed.  Since  this  lat- 
ter coil  is  not  connected  to  the  cell — ^the  source  of  current — it  follows 
that  the  current  which  deflects  the  needle  must  be  induced  current. 
If  the  inner  coil  remains  stationary  the  needle  is  not  affected,  but 
if  it  is  moved  then  deflection  occurs.  The  reason  for  this  induced 
current  may  be  explained  as  follows :  When  a  current  flows  through 
the  smaller  coil,  a  magnetic  field  with  lines  of  magnetic  force  trav- 
eling from  one  end  of  the  coil  to  the  other  through  the  air  is 


MAGNETISM  AND  COILS.  33 

set  up,  and  completely  surrounds  the  coil.  When  this  coil  is  drop- 
ped inside  of  the  large  coil  these  lines  of  force  are  cut  by  the  coils 
of  wire  in  the  larger  coil,  and  a  current  of  electricity  is  generated 
therein.  When  no  relative  motion  occurs  between  the  coils  no 
current  is  set  up  in  the  outer  coil.  In  order  for  a  current  to  be 
generated,  therefore,  lines  of  magnetic  force  must  "be  cut  by.  a  mov- 
ing conductor.  This  is  the  principle  upon  which  all  dynamo  elec- 
trical machines  work,  and  it  will  be  made  use  of  later  in  these 
lessons  in  explaining  the  operation  of  magnetos  and  dynamos  used 
for  ignition  purposes. 

Spark  Coils. — An  ordinary  spark  coil  used  for  make  and  break 
ignition  consists  of  a  single  coil  of  insulated  wire  wound  on  a  spool, 
in  the  center  of  which  there  is  a  core  of  soft  iron  wires.  This  core  is 
insulated  from  and  is  not  connected  electrically  with  the  coil.  When 
a  current  of  electricity  from  say  a  battery  flows  through  the  coil, 
the  core  of  soft  iron  becomes  magnetic  and  it  is  surrounded  by  lines 
of  magnetic  force.  The  passage  of  a  current  of  electricity  through 
this  magnetic  field  sets  up  a  counter  electro-motive  force  that  op- 
poses the  flow  of  current  and  consequently  the  current  does  not  in- 
stantly come  up  to  its  full  value,  but  builds  up  rather  slowly.  When 
the  current  is  broken,  as  when  the  igniter  trips,  the  lines  of  force 
decrease  slowly  and  this  induces  an  electro-motive  force  which  tends 
to  keep  the  current  flowing  in  the  coil.  This  self  induction,  as  it  is 
called,  between  the  loops  of  the  coil,  tends  to  maintain  the  current 
after  it  is  broken  and  the  result  is  a  bright  spark  at  the  igniter 
points.  The  coil  acts  as  a  sort  of  reservoir  for  the  accumulation  of 
a  certain  amount  of  electricity  to  be  used  when  the  circuit  is 
broken. 

A  coil  of  this  kind  must  always  be  connected  in  series  with  the 
cells  of  a  battery  for  the  ordinary  or  hammer  break  ignition,  in  order 
to  give  a  spark  of  sufficient  volume  and  intensity  to  ignite  the 
charge.  There  is  nothing  about  a  simple  coil  of  this  kind  to  wear 
out  and  if  taken  care  of  it  should  last  indefinitely.  If  water  gets  in 
between  the  turns  of  wire,  a  short  circuit  may  take  place,  or  the  in- 
sulation may  be  burned  through  by  a  heavy  current  at  some  time,  or 
possibly  a  wire  may  become  broken  inside  of  the  coil,  although  this  is 
a  rare  occurrence.  All  the  care  a  coil  requires  is  to  be  kept  in  a  dry 
place.  If  it  is  made  with  the  proper  kind  of  wire,  thoroughly  well 
insulated  and  kept  dry,  it  will  continue  to  give  good  service  in- 
definitely. 

In  the  next  lesson  we  will  discuss  the  jump  spark  coil  and  then 
take  up  magnetos  and  dynamos.  The  subjects  of  magnetism  and  in- 


34 


GASOLOGY. 


duction  presented  in  this  lesson  will  be  found  necessary  to  a  clear 
understanding  of  the  next  lesson. 

LESSON  X 

There  are  two  principal  methods  of  electric  ignition  in  common 
use,  one  known  as  the  hammer  break  method,  the  other  as  the  jump 
spark.  In  the  former  two  rods  pass  through  the  cylinder  walls  to 
the  interior  of  the  cylinder,  into  the  clearance  space.  One  rod  is 
carefully  insulated.  This  is  called  the  stationary  electrode.  The 
other  rod  is  not  insulated  and  is  movable.  At  the  right  instant 
in  the  stroke  some  moving  part  on  the  outside  of  the  engine,  driven 
from  the  main  shaft,  rotates  the  movable  electrode  until  the  two  ig- 
niter points  inside  the  cylinder  come  into  contact.  This  completes 

the  electric  circuit. 
Electricity  flows 
from  the  source  of 
current  through  the 
insulated  electrode, 
then  through  the 
movable  electrode  to 
the  points  of  the 
the  engine  frame 
and  back  through 
the  other  lead  wire 
to  its  source.  In 
this  connection  it 
may  be  well  to  note 
that  there  must  be  a 
complete  unbroken 
circuit  for  electrici- 
ty to  travel  along  or 
it  won't  travel.  At 
the  right  instant  a 
tripping  mechanism 
of  some  sort  throws 
electrodes  apart  and 
a  spark  is  formed  inside  of  the  cylinder  and  the  charge  is  ignited. 
In  the  case  of  the  jump  spark  there  are  no  moving  parts  inside 
of  the  cylinder.  The  current  which  ignites  the  charge  does  not 
have  a  complete  metallic  circuit  to  travel  in,  but  is  obliged  to  jump 
across  a  short  air  gap  inside  of  the  cylinder.  When  electricity  has 
to  bridge  a  gap  in  this  way  it  forms  an  arc  or  spark  and  it  is  this 


ft-is  metal  plate  loose,  on  shaft. 
~b-is  spring  con-tact  piece 
c-r,ielai  contact  fiece 
a  -insulating  cei/af  -fast-  ro  shaft. 


ElG.  10. 


MAGNETISM  AND  COILS.  35 

that  ignites  the  charge.  The  current  used  in  the  hammer  break 
system  could  not  jump  a  gap  because  it  has  not  pressure  enough,  or 
voltage  enough,  to  use  a  more  exact  term.  The  same  battery  would 
do  in  either  case,  but  a  different  spark  coil  is  necessary.  This  leads 
us  to  a  consideration  of  the  jump  spark  coil,  or  induction  coil,  as  it 
is  often  called. 

The  induction  coil,  known  also  as  the  Ruhmkorff  coil,  is  quite  dif- 
ferent from  the  simple  spark  coil  described  in  the  last  lesson.  It  con- 
sists essentially  of  a  core  of  very  soft,  thoroughly  annealed,  iron 
wires,  bound  together  and  covered  with  a  good  insulator  of  some 
sort,  which  forms  the  core.  Outside  of  this  there  is  a  coil  con- 
sisting of  a  few  turns  of  rather  coarse,  well  insulated  copper  wire  of 
about  14  gauge.  This  wire  is  connected  with  the  battery,  or  source 
of  current,  and  is  called  the  primary  circuit.  Outside  of  this  again, 
and  thoroughly  insulated  from  it,  there  is  another  coil  of  much  finer 
wire,  about  28  gauge,  called  the  secondary  coil.  This  coil  is  made 
up  with  a  great  many  turns  of  wire  and  makes  the  circuit  which  ig- 
nites the  charge.  The  general  arrangement  and  details  of  this  piece 
of  apparatus  are  shown  in  Fig.  10,  to  which  constant  reference  must 
be  made  to  complete  the  description. 

At  the  left  end  of  the  coil  there  is  shown  a  hammer,  H,  mounted 
on  a  flat  spring,  forming  what  is  called  the  vibrator.  When  at  rest 
the  spring  holds  the  hammer  against  the  screw,  W.  When  the 
switch  at  G  is  closed,  current  from  the  battery  can  flow  through 
wire  P,  up  through  D,  to  screw  W,  then  down  through  the  vibrator 
spring,  thence  through  wire  F,  to  the  primary  coil,  and  back  to  the 
battery  through  wire  M — S — the  engine — and  wire  P  to  the  battery, 
thus  completing  the  circuit.  In  practice  it  should  be  noted  that 
the  primary  circuit  is  closed  by  the  engine  at  the  right  instant. 
When  the  primary  circuit  is  closed  a  current  flows  around  the  pri- 
mary coil  and  the  core  becomes  an  electro  magnet.  It  immediately 
attracts  the  hammer  H  and  the  circuit  is  broken.  The  core  now 
loses  its  magnetism  and  the  vibrator  spring  throws  the  hammer  back 
and  the  circuit  is  again  completed.  As  long  as  the  circuit  remains 
closed  the  hammer  vibrates  back  and  forth  very  rapidly,  in  fact,  hun- 
dreds of  times  per  second,  each  time  opening  and  closing  the 
primary  circuit.  The  result  of  this  is  to  induce  a  current  in  the 
secondary  coil  of  very  much  higher  voltage,  which  has  power  enough 
to  jump  across  the  gap  in  the  spark  plug  at  K  to  the  engine  frame 
and  thence  back  to  the  secondary  coil. 

It  must  be  remembered  at  this  point  that  there  is  absolutely  no 
connection  electrically  between  the  primary  coil  and  the  secondary. 


36  GASOLOGY. 

The  question  then  arises,  how  is  a  current  formed  in  the  sec- 
ondary coil?  Kef  erring  to  lesson  IX,  this  statement  will  be  found: 
"In  order  for  a  current  to  be  generated,  therefore,  lines  of  magnetic 
force  must  be  cut  by  a  moving  conductor."  This  was  made  to  apply 
to  current  generated  by  mechanical  means,  not  chemically,  as  in  a 
battery.  Now,  it  might  have  been  stated  at  the  same  time  that  mo- 
tion is  only  relative.  For  instance,  suppose  we  wish  to  get  away 
from  a  certain  object;  there  are  two  ways  to  do  it.  Either  we  may 
move  ourselves  away  or  we  may  have  the  object  removed.  So  far  as 
we  and  the  object  are  concerned,  the  final  result,  that  of  mere 
separation,  will  be  as  well  accomplished  in  one  way  as  in  the  other. 
Motion,  therefore,  between  two  objects  is  relative.  Consequently, 
we  can  just  as  well  generate  current  by  moving  the  magnetic  field 
as  by  letting  it  stand  still  and  moving  the  conductor.  Now  that 
is  just  what  actually  happens  in  an  induction  coil.  We  showed  in 
the  last  lesson  that  if  a  current  of  electricity  were  sent  through  a 
coil  a  magnetic  field  was  instantly  set  up  around  the  coil.  If  this 
current  be  broken  the  magnetic  field  disappears.  If  now  the  magnetic 
field  be  made  to  change  rapidly  from  zero  to  a  maximum  in  intensity, 
as  it  does  due  to  the  vibrating  current  in  the  primary  coil,  the  re- 
sult is  a  moving  magnetic  field  and  a  stationary  conductor.  Thus, 
we  accomplish  the  same  result  as  we  would  obtain  with  a  stationary 
magnetic  field  and  a  moving  conductor.  Consequently,  a  current  will 
be  induced  in  the  secondary  coil,  and  this  current  will  have  a  much 
higher  voltage  than  the  voltage  in  the  primary  coil.  The  reason  for 
this  increase  in  voltage  is  due  to  the  difference  between  the  two  coils. 
If  the  secondary  coil  was  made  up  with  the  same  sized  wire  and  the 
same  length  of  wire  as  the  primary,  the  voltage  would  be  practically 
the  same,  but  since  it  is  made  up  of  very  much  finer  wire  the  volt- 
age or  pressure  is  increased,  but  the  amperage  or  amount  of 
current  is  decreased.  The  reason  for  this  may  be  explained  in  a 
rough  way  by  considering  water  flowing  through  a  pipe.  If  all  the 
water  that  flows  through  a  large  pipe  be  made  to  pass  through  a 
much  smaller  pipe,  the  velocity  in  the  smaller  pipe  must  be  very 
much  greater,  while  the  size  of  the  stream  or  amount  of  current  is 
proportionately  decreased. 

The  condenser  shown  in  the  diagram  is  placed  inside  of  the  box 
containing  the  coil  and  consists  of  a  number  of  sheets  of  tin  foil 
piled  one  on  top  of  the  other  and  insulated  from  each  other.  The 
ends  of  every  alternate  sheet  are  connected  at  K  and  the  other  sheets 
are  connected  with  wire  L.  The  object  of  this  device  is  to  demag- 
netize the  core  instantly  between  each  vibration  of  the  hammer, 


MAGNETISM  AND  COILS.  37 

to  prevent  an  intense  spark  between  the  hammer  and  contact  screw 
W,  to  increase  the  rapidity  and  extent  of  the  changes  or  vibrations 
in  the  primary  current,  and  by  changing  the  magnetism  of  the  core 
quickly  to  augment  the  current  in  the  secondary  coil.  The  manner 
in  which  all  this  is  accomplished  may  be  explained  thus:  When 
the  hammer  is  in  position,  shown  in  the  diagram,  the  condenser  is 
practically  inactive,  but  when  the  contact  with  W  is  broken  a  spark 
has  a  tendency  to  jump  across,  but  instead,  current  flows  from  D 
through  K  to  the  condenser  and  charges  it.  The  latter,  however, 
immediately  reacts  just  as  a  spring  reacts  when  struck  a  sharp 
blow  and  sends  a  small  current  backward  through  K — D — G — P,  the 
battery,  engine  wires  S  and  M,  thus  opposing  the  direction  of  the 
current  in  the  primary  coil  and  destroying  it  and  demagnetizing  the 
core. 

One  of  the  secondary  wires  S  is  attached  to  the  spark  plug  and 
the  other  to  some  part  of  the  engine  frame.  The  outer  casing  of  the 
spark  plug  is  connected  electrically  to  the  cylinder,  while  the  wire  that 
passes  through  the  plug  is  insulated  from  the  cylinder,  but  is  sep- 
arated from  the  metal  rim  at  R  by  only  about  1-32  of  an  inch. 
When  current  flows  in  the  secondary  coil  it  leaps  across  this  small 
air  gap  and  forms  the  spark.  As  long  as  the  vibrator  is  working 
a  stream  of  sparks  flows  across  this  air  gap. 

In  some  types  of  spark  coils  the  vibrator  instead  of  making  a 
large  number  of  oscillations  makes  only  one,  and  only  one  spark  is 
formed  inside  the  cylinder.  This,  of  course,  is  much  easier  on  the 
battery  as  it  takes  only  a  fraction  as  much  current. 


CHAPTER  IV 
DYNAMO— ELECTRIC  GENERATORS 


LESSON  XI 

The  sources  of  electrical  current  for  gas  engine  ignition  are  dry 
cell  batteries,  wet  cell  batteries,  storage  batteries,  dynamos  and 
magnetos.  We  have  already  discussed  the  first  two.  In  this  les- 
son we  will  turn  our  attention  to  dynamos  and  magnetos,  reserving 
storage  batteries  for  a  subsequent  lesson. 

Batteries  generate  electrical  energy  by  chemical  action.  Dyna- 
mos and  magnetos  generate  electrical  energy  by  mechanical  means. 

In  the  case  of  bat- 
teries a  definite 
quantity  of  certain 
chemicals  is  con- 
sumed in  generating 
a  given  amount  of 
electricity.  While 
in  the  case  of  a  dy- 
namo or  a  magneto 
a  definite  amount  of 
work  must  be  ex- 
pended to  produce 
a  given  amount  of 
electricity.  Batter- 
ies transform  chem- 
ical energy  into 
electrical  energy, 
while  dynamos  and 
magnetos  transform  mechanical  energy  into  electrical  energy.  The 
equivalent  electrical  energy  that  is  generated  in  either  case  will  be 
less  than  either  the  chemical  energy  or  the  mechanical  energy  that 
produces  it.  In  other  words,  there  is  always  some  loss  in  the 
transformation  process,  even  under  the  most  favorable  conditions. 
When  a  coil  of  wire  is  moved  across  a  magnetic  field  in  such  a 
way  as  to  cut  the  lines  of  force  at  right  angles,  an  electric  current 
is  set  up  in  the  coil.  This  is  the  fundamental  principle  of  opera- 
tion of  both  dynamos  and  magnetos. 


DYNAMO-ELECTRIC  GENERATORS. 


Figure  12  is  a  diagram  which  illustrates  the  method  by  which  this 
principle  is  applied  in  a  practical  way.  P  P  are  the  pole  pieces;  C  is 
the  armature,  which  is  keyed  to  a  shaft  D  and  which  rotates  be- 
tween the  pole  pieces.  The  core  of  the  armature  is  made  up  of  a 
large  number  of  thin  iron  punchings  (see  Fig.  14)  having  slots  on  the 
circumference  to  carry  the  coils  of  wire.  The  completed  armature  is 
shown  in  Fig.  13.  The  loops  of  wire  are  wound  lengthwise  around  the 
armature  and  the  ends  are  soldered  to  copper  segments,  S.  One  end 
of  the  loop  of  wire 
is  soldered  to  a 
segment  on  one  side 
of  the  cylinder  and 
the  other  end  to  a 
segment  on  the  oth- 
er side.  These  cop- 


per     segments     are 
insulated  from  each 

other  with  strips  of  mica,  and  from  the  shaft  by  a  mica  sleeve.  All 
of  these  copper  strips  taken  together  are  called  the  comnmtator. 
F  F  are  the  field  pieces.  They  are  soft  iron  columns  around  which 
there  is  wound  a  continuous  coil  of  insulated  copper  wire.  One  end 
of  this  coil  is  connected  to  one  of  the  brushes  h,  the  other  is  con- 
nected to  the  outside  circuit  and  through  that  to  the  other  brush. 
The  brushes  collect  the  current  from  the  armature,  pass  it  through 
the  field  coils,  and  the  external  circuit  and  back  again  to  the  other 

brush,  thus  completing  the  cir- 
cuit through  the  armature  coil  that 
the  two  brushes  happen  to  be  in 
contact  with  at  the  given  instant. 
The  above  description  applies  to 
what  is  known  as  a  direct  current 
series  wound  dynamo. 

The  little  arrows  pointing  to- 
ward the  center  of  the  armature 
represent  the  lines  of  magnetic 
force  which  are  supposed  to  be 
constantly  passing  between  the 
pole  faces  PP.  We  will  call  the 
left  pole  the  positive  or  north  pole 
N,  and  the  other  the  south  pole  8. 
If  the  armature  is  rotated,  a  coil 
such  as  a  1}  cuts  all  the  lines  of  force  and  a  current  of  electricity 
will  be  induced  in  it.  While  the  conductor  is  passing  the  neutral 


40  GASOLOGY. 

region,  at  the  gap  between  the  pole  faces,  no  current  will  be  gen- 
erated. Current  is  generated  only  when  lines  of  force  are  cut, 
and  will  be  greatest  at  the  points  m  and  n.  When  the  coil  passes 
the  north  pole,  revolving  in  the  direction  shown  by  the  large  ar- 
row, the  current  is  flowing  toward  the  segment  under  the  top  brush, 
but  when  it  cuts  the  lines  of  force  opposite  the  south  pole  the  di- 
rection of  current  is  reversed.  By  placing  the  brushes  just  at  the 
point  where  the  current  reverses  in  direction  a  continuous  current, 
flowing  always  in  the  same  direction,  will  be  produced  in  the  ex- 
ternal circuit.  This,  then,  is  the  purpose  of  the  commutator; 
namely,  to  produce  a  direct  current,  one  that  does  not  change  its 
direction  in  the  external  circuit.  When  a  current  flows  through  the 
field  coils  around  Ff  the  fields  and  pole  pieces  become  strong  electro- 
magnets, thus  increasing  the  magnetic  induction,  or  number  of 
lines  of  force,  and  consequently  a  stronger  current  is  generated 
in  the  armature  coils.  The  larger  the  current  flowing  through  the 
field  coils',  therefore,  the  greater  will  be  the  strength  of  the  mag- 
netic field  until  what  is  known  as  the  saturation  point  is  reached, 
or  the  point  at  which  no  more  lines  of  force  are  possible.  The  faster 
a  dynamo  is  run  the  greater  the  current  that  will  be  generated.  In 
order  to  protect  the  dynamos  used  in  gas  engine  ignition  from  too 
heavy  currents  they  are  provided  with  a  governor  that  will  not 
allow  them  to  run  much  faster  than  about  1,400  revolutions  per 
minute.  At  this  speed  they  will  generate  about  eight  or  ten  amperes 
with  a  voltage  of  about  ten.  Since  it  is  hardly  possible  to  make 
them  run  fast  enough  by  turning  the  fly  wheel  by  hand,  a  dry  cell 
battery  is  required  for  starting.  When  the  engine  comes  up  to 
speed  this  may  be  switched  off  and  the  dynamo  switched  on  to  the 
ignition  circuit.  Some  of  these  dynamos  must  be  run  in  connection 
with  a  spark  coil  for  make  and  break  ignition  and  some  generate 
a  current  strong  enough  not  to  require  any  coil.  For  jump  spark  ig- 
nition the  coil  is  necessary,  except  with  some  forms  of  magnetos. 
These  little  direct  current  dynamos  are  made  very  compact  and 
some  of  them  are  entirely  enclosed  from  the  dust  by  a  metal  casing. 
They  do  not  require  very  much  attention  except  an  occasional  turn- 
ing of  the  brushes  with  a  file  and  polishing  of  the  commutator  with 
a  bit  of  fine  sand  paper.  Emery  paper  must  not  be  used  for  this 
purpose.  The  commutator  must  not  be  oiled.  All  the  lubrication 
that  is  needed  is  a  little  on  the  armature  shaft  bearings.  For  ig- 
nition purposes  on  stationary  gas  engines  they  are  quite  satisfactory. 
Where  they  are  used  on  road  engines,  difficulty  may  arise  through 
some  of  the  wire  connections  becoming  loose.  This  must  be  guarded 
against  by  frequent  inspection. 


DYNAMO-ELECTRIC  GENERATORS. 


41 


LESSON  XII. 

MAGNETOS. 

The  fields  of  a  magneto  are  made  of  permanent  mag- 
nets. Those  of  a  dynamo,  such  as  we  described  in  the  last  lesson, 
are  electro-magnets.  This,  then,  is  the  essential  difference  between 
these  two  types  of  generators.  The  dynamo  is  provided  with  a  field 
winding,  that  is,  a 
coil  of  wire  which 
surrounds  the  field 
pieces  and  either  all 
or  a  part  of  the  cur- 
rent generated  flows 
through  this  wind- 
ing. This  is  what 
generates  the  mag- 
netic  field  between 
the  pole  pieces.  In  the  magneto  there  is  no  winding  around  the 
field  pieces.  These,-  instead  of  being  made  of  soft  iron,  are  made 
of  hardened  steel  and  permanently  magnetized.  The  armature  is  also 
made  differently.  It  consists  of  an  H-shaped  piece  of  soft  iron  around 
which  a  single  continuous  coil  of  wire  is  wound  parallel  with  the 
axis.  Figure  15  shows  the  simplest  style  of  magneto  armature,  and 

Fig.  16  shows  an  end  view  of  the  com- 
plete machine  assembled. 

The  armature  fits  very  closely  be- 
tween the  pole  pieces,  having  a  clearance 
of  only  about  one  one-hundredth  of  an 
inch.  The  pole  pieces  P  are  made  of 
soft  iron  and  the  lines  of  force  pass 
from  the  positive  pole  to  the  negative 
through  the  soft  iron  H  of  the  armature. 
The  manner  in  which  the  current  is 
generated  will  now  be  described. 

When  the  armature  is  in  the  position 
shown  in  Fig.  16,  the  lines  of  force  pass 
from  one  pole  piece  to  the  other  through 
the  soft  iron  neck  of  the  armature, 
since  that  is  the  only  path  they  can 
travel.  The  brass  plate  at  the  bottom 
is  not  a  conductor  of  magnetism  and 
no  lines  of  magnetism  can  pass  from  one  pole  to  the  other  through 


42 


GASOLOGY. 


it.  The  armature  acts  just  like  the  keeper  or  flat  piece  of  iron  that 
is  laid  across  the  ends  of  a  horse-shoe  magnet.  When  the  armature 
is  not  in  position  the  lines  of  force  will  pass  through  the  air  along 
the  lines  of  least  resistance,  through  a-a  or  ~b-~b.  But  the  greater 
number  will  pass  between  the  points  fc-Z>  since  these  are  the  nearest 

together.  When  the  armature  is  in  the 
position  shown  in  Fig.  16,  all  of  them 
will  pass  through  the  neck  of  the  arma- 
ture, as  before  stated. 

When  the  armature  is  turned  to  the 
position  shown  in  Fig.  17,  the  lines  of 
force  are  distorted,  as  shown,  but  still 
flow  through  the  neck  N.  But  when  the 
armature  is  turned  still  farther  so  that 
N  stands  vertical,  as  in  Fig.  18,  the  lines 
of  force  no  longer  flow  through  Nf  but 
take  two  paths,  one  across  a-a,  the  other 
~b-~b,  since  these  are  the  paths  of  least 
resistance. 

When  the  lines  of  force  are  flowing 
through  the  neck  N,  as  in  Fig.  16,  the 
soft  iron  core  is  strongly  magnetized; 
but  when  the  armature  revolves  to  the 
position  of  Fig.  18,  N  is  demagnetized.  In  this  way  the  magnetism 
of  the  armature  varies  from  a  maximum,  when  the  neck  N  is  hori- 
zontal, to  almost  nothing  when  it  is  ver- 
tical. As  the  armature  revolves,  there- 
fore, there  are  rapid  changes  in  the  mag- 
netic field  through  which  the  armature 
coil  is  passing.  We  have,  then,  a  va- 
riable magnetic  field,  just  as  we  have  in 
an  induction  coil,  and  the  result  is 
that  a  current  of  electricity  is  induced  in 
the  armature  coil.  Since  the  greatest 
change  in  magnetism  occurs  when  the 
neck  N  is  vertical,  it  follows  that  the 
strongest  current  will  be  induced  each 
time  N  stands  in  a  vertical  position,  and 
the  weakest  when  N  is  horizontal.  Twice 
in  each  revolution  of  the  armature  the 
current  will  be  a  maximum,  and  twice  it 
will  be  a  minimum. 


DYNAMO-ELECTRIC  GENERATORS.  43 

Since  the  current  is  variable,  it  follows  that  ignition  must  be  made 
to  occur  when  armature  stands  with  its  neck  in  a  vertical  position. 
This  is  the  only  position  in  which  current  is  strong  enough  to  pro- 
duce a  sufficiently  strong  spark. 

It  is  perfectly  clear  in  view  of  the  above  explanation  that  the 
magneto  must  be  in  exact  step  with  the  engine  in  order  to  ignite  the 
charge  at  the  right  time.  It  must,  therefore,  be  driven  by  the  crank 
shaft  of  the  engine  by  some  positive  means.  If  it  were  driven  by  a 
friction  pulley  or  by  a  belt  in  the  manner  that  the  dynamo  described 
in  the  last  lesson  was  driven,  it  would  soon  be  out  of  time  with  the 
crank  shaft  on  account  of  slippage  between  the  friction  surfaces. 
The  only  way  to  drive  the  armature  of  a  magneto,  where  it  makes  a 
complete  revolution,  is  by  means  of  toothed  gearing. 

A  consideration  of  the  principles  of  action  of  a  magneto  will  show 
the  reader  that  it  is  not  necessary  for  the  armature  to  make  a  com- 
plete revolution.  If  it  is  made  to  turn  from  a  vertical  position  to  a 
horizontal  position  and  then  is  whirled  swiftly  back  to  the  vertical, 
say  by  means  of  strong  springs,  a  sufficient  current  will  be  set  up 
to  ignite  the  charge.  Some  magnetos  are  built  on  this  principle 
and  a  push  rod  operated  by  a  cam  on  the  crank  shaft  or  on  an  aux- 
iliary shaft,  if  it  is  a  four-cycle  engine,  will  oscillate  the  armature  of 
the  magneto  at  the  right  time. 

There  are  two  types  of  magnetos,  one  known  as  the  low  tension 
type  and  the  other  as  the  high  tension.  The  one  just  described  is  a 
low  tension  magneto  used  for  make  and  break  ignition.  A  mag- 
neto of  this  type  is  wound  to  deliver  current  at  from  100  to  150 
volts. 

High  tension  magnetos,  strictly  speaking,  are  provided  with  two 
windings,  one  of  a  few  turns  of  coarse  wire  and  the  other  of  a 
large  number  of  turns  of  fine  wire.  Magnetos  of  this  type  generate 
current  at  a  high  voltage,  ranging  from  10,000  to  20,000.  Such 
high  tension  magnetos  are  used  only  for  jump  spark  ignition.  Low 
tension  magnetos,  in  conjunction  with  a  spark  coil,  are  used  more 
frequently  than  the  high  tension  magnetos  for  jump  spark  ig- 
nition. 

In  the  simple  magneto  just  described,  one  end  of  the  coil  wire  is 
grounded  on  the  metal  of  the  armature  and  the  other  end  is  at- 
tached to  a  metal  rod  passing  through  the  armature  shaft.  This  rod 
is  insulated  from  the  shaft  by  a  hard  rubber  bushing.  There  is, 
therefore,  only  one  terminal,  and  if  this  is  connected  to  the  insu- 
lated electrode,  the  current  can  pass  back  to  the  armature  of  the 


44  GASOLOGY. 

magneto  through  the  engine  frame  when  the  igniter  points  are  in 
contact,  since  the  magneto  itself  is  connected  directly  to  the  metal 
frame  work  of  the  engine. 

LESSON  XIII. 

The  general  principles  of  magneto  ignition  were  outlined  in  the 
last  lesson.  A  little  study  will  show  the  reader  that  a  magneto  of 
the  kind  therein  illustrated  is  a  very  simple  machine.  There  are 
comparatively  few  parts,  there  is  only  one  winding,  that  on  the 
armature,  and  there  are  few  wire  connections  to  work  loose.  In 
fact,  there  are  only  two  connections,  one  to  the  armature  shaft  and 
the  other  to  a  ring  or  bushing  which  is  insulated  from  the  shaft. 
The  current  is  taken  off  by  means  of  a  brush  or  metal  contact  point 
from  this  bushing. 

On  account  of  the  simplicity  of  magnetos,  and  their  general  re- 
liability in  case  of  rough,  hard  service,  they  are  used  quite  exten- 
sively on  automobiles.  Two  types  are  in  general  use,  one  the  low 
tension  magneto  which  works  through  a  make  and  break  igniter, 
or  in  conjunction  with  a  spark  coil  for  jump  spark  ignition.  The 
other  type  of  magneto  is  known  as  a  high  tension  magneto.  In  this 
machine  the  armature  is  provided  with  two  windings,  one  consisting 
of  a  few  turns  of  coarse  wire,  the  other  of  many  turns  of  fine 
wire.  This  secondary  winding  is  identical  with  the  secondary  wind- 
ing on  an  induction  coil,  and  like  it,  is  insulated  from  the  primary 
winding.  Magnetos  of  this  type  are  expensive  and  are  used  only  on 
automobiles. 

The  higher  the  speed  at  which  a  magneto  is  run,  the  higher  will 
be  the  voltage  and  the  hotter  the  spark.  At  slow  speeds  the  spark 
will  be  quite  thin  and  weak,  while  at  high  speed  it  will  be  almost 
a  flame.  This  is  particularly  desirable  because  at  high  speeds  igni- 
tion and  combustion  must  be  rapid  in  order  to  be  completed  at  the 
instant  the  piston  passes  its  dead  center  position.  When  a  battery 
is  used,  the  spark  must  be  advanced  greatly  at  high  speeds.  While 
it  is  true  that  the  spark  of  the  magneto  must  also  be  advanced,  it 
need  not  be  advanced  so  much  as  a  battery  spark  on  account  of  its 
greater  intensity. 

Magneto  Troubles. — Like  all  other  mechanical  devices,  the  magneto 
is  liable  at  times  to  give  trouble.  If  ignition  fails  the  first  thing  to 
do  is  to  test  the  magneto  and  see  if  it  gives  a  current.  An  easy 
way  to  do  this,  though  some  may  find  it  a  trifle  severe,  is  to  dis- 
connect the  magneto  from  the  ignition  system,  then  connect  a  piece 


DYNAMO-ELECTRIC  GENERATORS.  45 

of  wire  to  its  terminal  and  hold  the  free  end  with  the  bare  fingers 
of  one  hand  while  the  other  hand,  also  bare,  is  in  contact  with  some 
bright  metallic  part  of  the  engine.  Now  have  an  assistant  turn  the 
magneto  quickly  by  turning  the  fly  wheel  of  the  engine.  If  the  mag- 
neto is  in  good  shape  a  shock  will  be  felt.  By  holding  the  free  end  of 
the  wire  against  a  toothed  wheel  while  some  one  turns  the  fly  wheel 
around  quickly,  a  spark  will  be  formed  as  the  contact  is  broken  be- 
tween the  teeth  at  some  point  in  the  stroke,  if  the  magneto  is 
working  right.  This  method  of  testing  is  just  as  satisfactory  as  the 
first  method  and  a  little  less  severe  on  the  operator.  If  no  current  is 
being  generated,  it  shows  that  something  is  wrong  with  the  magneto. 
Perhaps  some  oil  or  dirt  has  accummulated  under  the  brush  or  spring 
that  leads  the  current  from  the  armature.  Or,  it  may  be  that  the 
armature  wire  is  broken.  This  does  not  often  occur  and  if  it  does, 
the  break  will  be  found  where  it  connects  to  the  insulated  rod  passing 
through  the  shaft.  A  drop  of  solder  will  repair  the  mischief  at  this 
point. 

Care  should  be  taken  in  making  any  repairs  on  a  magneto  where 
the  magneto  has  to  be  taken  apart.  A  little  carelessness  or  ignorance 
may  easily  spoil  a  valuable  machine.  The  armature  acts  the  same 
as  a  keeper  on  a  toy  horseshoe  magnet.  It  provides  an  easy  path  for 
the  lines  of  magnetic  force.  If  this  is  taken  away,  the  lines  of 
force  pass  through  the  air  and  since  they  meet  considerable  resist- 
ance some  are  lost  and  the  magneto  becomes  permanently  weakened. 
On  the  other  hand,  if  the  armature  is  always  in  place,  a  magnet  will 
retain  its  magnetism  indefinitely  unless  abused  in  some  other  way, 
such  as  being  heated  to  a  high  temperature.  The  armature  of  a 
magneto  also  acts  as  a  path  for  the  lines  of  magnetic  force.  If  it  is 
removed  either  the  space  between  the  pole  pieces  must  be  filled  with 
a  piece  of  soft  iron  or  a  heavy  piece  of  soft  iron  must  be  laid  across 
the  pole  pieces  under  the  arch  of  the  magneto  to  provide  a  path  for 
the  lines  of  force.  Unless  a  man  is  well  informed  about  magnetos  he 
had  better  not  take  them  apart  or  try  to  make  extensive  repairs. 
In  cases  where  the  difficulty  is  not  easy  to  detect,  or  where  consider- 
able repairing  must  be  done,  it  is  better  for  the  ordinary  unskilled 
individual  to  turn  the  job  over  to  a  good  electrician. 

If,  after  the  test  of  the  magneto,  it  has  been  found  to  be  in  good 
condition,  the  trouble  will  be  found  in  some  of  the  connections, 
probably  in  the  spark  plug.  The  most  prevalent  cause  of  trouble  at 
this  point  is  due  to  the  fouling  of  the  igniter  points.  A  deposit  of 
carbon,  or  of  oil,  often  forms  on  the  points  which  will  prevent  the 
passage  of  a  spark.  Poor  lubricating  oil,  which  has  a  flashing  point 


46  GASOLOGY. 

somewhat  too  low,  causes  trouble  since  some  of  it  will  be  consumed 
while  a  part  will  merely  char  and  form  a  deposit  of  carbon.  Too 
much  lubricating  oil,  even  of  good  quality,  will  produce  as  bad  re- 
sults. A  plug  with  oil  dripping  from  the  points  will  not  give  a 
spark.  When  a  plug  is  found  to  be  in  this  condition,  or  covered  with 
a  deposit  of  soot  or  carbon,  it  should  be  washed  with  gasoline.  The 
gasoline  dissolves  the  carbon  and  loosens  it  so  that  it  can  readily  be 
wiped  off.  The  distance  between  the  points  of  a  spark  plug  should 
not  exceed  one  thirty-second  of  an  inch,  and,  in  general,  should  be 
only  about  one-half  this  amount.  It  frequently  happens  that  the 
points  become  bent  so  that  they  either  touch  or  else  are  too  far  apart. 
An  inspection  of  the  plug,  of  course,  will  show  if  either  one  of  these 
things  causes  the  trouble,  and  the  remedy  is  evident.  A  crack  in 
the  insulation  of  the  plug  often  causes  trouble.  Moisture  is  apt  to 
gather  in  the  crack,  thus  making  an  easy  path  for  the  passage  of 
the  current  to  the  engine  frame  instead  of  arching  or  sparking 
across  the  gap  and  producing  a  spark  as  it  should.  The  obvious 
remedy,  of  course,  is  to  put  in  a  new  plug.  One  of  the  best  ways  to 
test  a  plug  is  to  put  in  a  new  one  and  try  it.  If  it  works  all  right, 
and  the  old  one  does  not,  it  shows  the  old  one  is  not  in  good  con- 
dition. When  jump  spark  ignition  is  used,  the  man  in  charge 
should  see  to  it  that  there  are  one  or  two  new  plugs  on  hand  in 
case  of  trouble  with  the  one  in  use. 

Where  a  magneto  is  used  for  hammer  break  ignition,  as  it  fre- 
quently is,  it  may  fail  to  act  if  the  igniter  points  are  in  poor  con- 
dition. A  deposit  of  soot  on  the  points  will  cause  failure;  also  if 
the  movable  electrode  sticks  in  contact  with  the  stationary  electrode, 
or  if  the  insulation  of  the  stationary  electrode  is  broken  down.  A 
short  circuit,  due  to  any  cause,  such,  for  example,  as  the  wearing  of 
the  insulation  from  the  wire  that  leads  to  the  stationary  electrode 
at  the  point  where  it  crosses  the  engine  frame,  will  cause  failure  of 
ignition. 

Sometimes  an  engine  fitted  with  a  magneto  will  run  well  at  low 
speed  and  never  miss  a  charge,  but  when  the  speed  is  increased  it 
will  begin  to  miss.  The  reason  for  this  is  generally  a  break  in  the 
insulation  of  the  stationary  electrode,  which  is  not  serious  enough 
to  cause  a  leak  of  current  when  the  voltage  is  low,  as  it  is  when 
the  magneto  runs  slowly,  but  which  allows  the  current  to  pass 
through  the  break  to  the  engine  frame  when  the  voltage  is  high. 
The  obvious  remedy  in  this  case,  of  course,  is  to  either  repair  the 
insulation  or  get  a  new  igniter  block.  When  several  cylinders  are 
fired  from  the  same  magneto,  it  may  happen  that  only  one  of  the 


DYNAMO-ELECTRIC'  GENERATORS.  47 

igniter  blocks  is  out  of  order,  in  which  case  all  the  cylinders  will 
fire  at  slow  speed,  and  this  one  will  miss  when  the  speed  is  high. 
The  manner  of  testing  to  determine  which  one  is  at  fault  is  to  dis- 
connect the  ignition  system  from  all  cylinders  and  try  to  run  at  high 
speed  first  with  one  cylinder  and  then  with  another  until  the  faulty 
igniter  is  located. 


CHAPTER  V 
STORAGE  BATTERIES 

LESSON  XIV. 

It  has  already  been  pointed  out  in  these  lessons  that  the  sources 
of  current  for  electrical  ignition  may  be  classed  under  two  heads; 
chemical  and  mechanical.  Chemical  generators  are  again  sub- 
divided into  two  classes;  primary  batteries,  made  up  with  either 
wet  cells  or  dry  cells,  and  secondary  batteries,  called  storage  bat- 
teries or  accummulators.  Mechanical  generators  may  be  either 
dynamos  or  magnetos. 

Glancing  back  over  previous  lessons  in  which  primary  cells  have 
been  described,  we  will  find  that  a  primary  cell  consists  of  two 
elements  submerged  in  a  liquid  or  paste  called  the  electrolyte.  The 
elements  are  usually  carbon  and  zinc,  but  very  often  they  are  copper 
oxide  and  zinc.  Either  dry  cells  or  wet  cells  may  be  made  up  with 
either  of  these  pairs  of  elements. 

The  electrolyte  for  the  first  named  elements  is  generally  a  solu- 
tion of  sal-ammoniac  and  water.  For  the  last  named  elements 
caustic  soda  and  water  are  used. 

In  all  primary  cells  that  we  have  considered,  electricity  is  generated 
by  the  destruction  of  the  zinc  element  and  the  quantity  of  current 
generated  in  a  given  time  is  proportional  to  the  amount  of  zinc 
consumed. 

When  zinc  is  acted  upon  by  the  electrolyte,  bubbles  of  hydrogen 
gas  form  on  the  other  element.  The  formation  of  these  bubbles 
is  called  polarization  and  the  effect  is  to  weaken  the  voltage  and 
current  output  of  the  cell.  In  all  well  constructed  cells  some  means 
are  used  to  prevent  polarization.  In  dry  cells  manganese  dioxide  is 
placed  in  contact  with  the  carbon  element  to  prevent  polarization, 
but  it  is  only  partially  successful.  It  is  in  consequence  of  polari- 
zation that  dry  batteries  become  weaker  with  continuous  use.  If 
they  are  allowed  to  rest  for  a  time  the  bubbles  of  hydrogen  unite 
with  the  oxygen  of  the  manganese  dioxide,  the  cell  is  depolarized  and 
it  is  quite  fresh  and  strong  again. 

It  is  quite  evident  in  view  of  the  tendency  of  the  dry  cell  to  polar- 
ize that  it  is  not  adapted  to  continuous  service  or  for  ignition  pur- 
poses for  a  high  speed  four  cylinder  engine  such  as  is  used  in  many 
automobiles. 


STORAGE  BATTERIES.  49 

In  the  Edison  cell  polarization  is  largely  prevented  by  putting  a 
depolarizing  agent  such  as  manganese  dioxide  in  the  copper  oxide 
plate.  Since  the  chemical  action  in  a  liquid  is  more  rapid  than  in 
a  paste  it  follows  that  the  liquid  cell  is  better  adapted  to  continuous 
service,  or  nearly  continuous  service,  than  is  the  dry  cell,  because 
depolarization  takes  place  more  rapidly. 

Briefly,  we  have  considered  the  action  of  primary  cells  and  are  now 
ready  to  look  into  the  construction  and  operation  of  secondary  cells. 

The  storage  cell  consists  of  two  elements,  as  in  the  case  of  a  pri- 
mary cell,  dipped  into  an  electrolyte.  Unlike  the  primary  cell  it 
can  not  give  off  electrical  energy  in  its  original  state  when  the  cir- 
cuit is  closed.  The  storage  cell  must  first  be  charged  with  electrical 
energy  from  some  source  of  current  like  a  dynamo  before  it  in  turn 
can  be  used  as  a  source  of  current.  The  charging  of  a  storage 
battery  sets  up  chemical  action  in  the  elements  and  in  the  electrolyte 
which  causes  changes  in  the -material  of  which  they  are  formed. 
The  electrical  energy  of  the  charging  current  is  thus  changed  into 
chemical  energy  which  in  turn  works  certain  changes  in  the  elec- 
trolyte and  in  the  elements.  If  now  the  newly  charged  storage 
battery  be  put  on  a  closed  circuit,  that  is,  connected  up  to  deliver 
current,  chemical  action  will  again  take  place,  but  in  a  reverse  direc- 
tion. The  electrolyte  and  elements  will  be  changed  back  to  their  orig- 
inal condition  and  nearly  as  much  electricity  will  be  delivered  from 
the  battery  as  was  put  into  it  in  the  first  place.  The  current  produced 
by  the  battery  will  flow  in  the  opposite  direction  to  the  charging 
current. 

A  storage  battery  may  be  charged  and  discharged  a  great  many 
times,  and  if  properly  cared  for  will  last  for  a  number  of  years. 
In  this  respect  it  differs  from  primary  batteries  which  can  not  be 
recharged  ordinarily,  but  must  be  renewed  when  run  down. 

There  are  several  substances  that  can  be  used  for  the  electrodes 
and  electrolytes  of  a  storage  battery,  but  practically  all  that  are  now 
on  the  market  use  some  compound  of  lead  for  the  former  and  sul- 
phuric acid  and  water  for  the  latter.  One  electrode  is  composed  of 
sponge  lead  and  the  other  of  lead  peroxide.  The  former  is  the 
negative  plate,  the  latter  the  positive  plate  since  it  is  from  this  plate 
the  current  flows  out. 

Since  lead  is  the  only  cheap  metal  that  will  withstand  sulphuric 
acid,  it  is  used  to  form  the  support  for  the  electrodes.  The  surface 
of  the  cast  lead  plates  is  filled  with  grooves  and  a  paste  of  lead  oxides 
is  forced  in  under  pressure  and  then  treated  to  form  either  sponge 
lead  or  lead  peroxide  as  the  occasion  demands. 


50  GASOLOGY. 

A  number  of  the  plates  after  being  prepared  in  the  way  above 
described  are  placed  side  by  side  in  a  glass  jar,  or,  if  the  battery 
is  to  be  used  for  automobile  ignition,  the  containing  vessel  may  be 
made  of  hard  rubber,  or  of  wood  lined  with  rubber  or  sheet  lead.  The 
electrodes  are  carefully  insulated  from  each  other  and  from  the 
bottom  of  the  containing  vessel  to  prevent  any  possibility  of  short 
circuiting  either  by  contact  with  each  other  or  by  dipping  into  the 
sediment  which  may  form  in  the  bottom  of  the  vessel.  The  top  of 
the  vessel,  if  it  be  an  automobile  cell,  is  covered  with  a  hard  rubber 
cover  which  is  sealed  in  place  with  hard  pitch.  A  small  vent  hole 
in  the  cover  allows  the  gas  to  escape,  but  is  too  small  to  allow  much 
of  the  electrolyte  to  spill  even  if  the  cell  is  turned  bottom  side  up. 
The  two  terminals  come  up  through  the  cover  and  a  suitable  opening 
is  provided  through  which  the  electrolyte  may  be  introduced.  This 
opening  is  stopped  with  a  rubber  cork. 

Each  side  of  each  positive  plate  should  face  a  negative  plate,  thus 
making  it  necessary,  generally,  to  have  one  more  of  the  latter  than 
of  the  former.  Automobile  ignition  batteries  consist,  generally, 
of  two  cells.  When  this  form  of  current  generator  is  used  it  is 
customary  to  have  two  batteries  connected  to  the  engine  through 
a  double  point  switch  so  that  either  one  may  be  connected  in  as  the 
operator  desires.  Since  a  storage  battery  does  not  recover  by  standing 
idle,  like  a  primary  battery,  one  battery  should  be  used  until  the 
engine  begins  to  miss,  when  it  should  be  cut  out  and  the  other  bat- 
tery put  in  service. 

The  chemical  reactions  in  a  storage  battery  are  not  yet  thoroughly 
understood,  but  it  is  generally  agreed  that  when  the  cell  is  being 
charged,  lead  peroxide  is  formed  on  the  positive  plate  and  metallic 
lead  on  the  negative  plate.  During  discharge,  lead  sulphate  is 
formed  on  both  plates.  Lead  sulphate  is  a  white  substance  and  has 
no  electrical  conductivity.  If  the  cell  is  allowed  to  discharge  too 
much,  an  excessive  amount  of  this  substance  is  formed  and  the  cell 
can  not  be  easily  recharged  again.  Care  must  be  taken  not  to  al- 
low the  voltage  of  a  dry  cell  to  run  down  too  low  or  it  may  be  ruined. 
When  the  voltage  of  a  cell  falls  to  1.8  volts  on  discharge,  it  is  time 
to  put  it  out  of  commission  until  it  can  be  recharged. 

Another  reason  why  the  voltage  must  not  be  allowed  to  rtm  down 
below  1.8  is  that  the  formation  of  lead  sulphate  causes  an  increase 
of  volume  which  causes  the  plates  to  buckle  and  the  paste  to  crack 
and  fall  out  of  the  grooves  in  the  plate. 

Charging  a  Storage  Battery. — Direct  current  must  be  used  to 
charge  a  storage  battery.  Alternating  current  can  not  be  used  ex- 


STORAGE  BATTERIES.  51 

cept  in  connection  with  a  rectifier  which  changes  the  alternating 
current  to  direct.  The  voltage  of  the  charging  current  used  for 
charging  a  single  cell  must  not  exceed  2.5  volts.  A  two  cell  battery 
would  require  a  current  strength -of  5  volts.  The  positive  wire  of 
the  charging  line  must  be  connected  with  the  positive  pole  of  the 
battery.  If  the  charging  current  is  passed  the  wrong  way  into  the 
cell,  the  cell  will  be  ruined.  The  positive  and  negative  terminals 
can  be  determined  by  means  of  a  voltmeter.  If  this  is  not  at  hand, 
draw  off  some  of  the  electrolyte  and  place  in  a  glass  vessel.  Con- 
nect two  strips  of  lead  to  the  terminals  of  the  battery  and  insert 
them  in  the  liquid,  taking  care  they  do  not  touch.  The  strip  that 
turns  brown  is  connected  to  the  positive  terminal. 

In  charging  a  battery  remove  the  vent  plug  from  each  cell  to  allow 
the  gas  which  forms  to  escape.  This  gas  is  hydrogen  gas  and  is 
highly  inflammable  and  care  must  be  taken  not  to  bring  a  naked 
flame  near  the  cells  while  being  charged.  The  completion  of  the 
charge  will  be  indicated  by  the  boiling  or  gasing  of  the  electrolyte, 
and  the  charging  current  should  be  shut  off  about  twenty  minutes 
after  this  begins.  At  this  time  the  voltage  of  each  cell  will  be  about 
2.5  volts.  A  slight  overcharge  will  not  hurt  a  cell,  but  if  charging 
is  carried  too  far  lead  sulphate  will  form  and  the  cell  may  be  in- 
jured or  even  ruined. 

LESSON  XV. 

The  electrolyte  is  made  up  with  sulphuric  acid  and  water,  using 
one  part  of  chemically  pure  acid  to  three  or  four  parts  of 
distilled  water  or  clean  rain  water.  The  acid  should  be  add- 
ed to  the  water  slowly,  at  the  same  time  stirring  the  mixture 
vigorously.  The  addition  of  sulphuric. acid  to  water  generates  heat 
and  care  must  be  taken  not  to  pour  water  into  the  acid,  because  heat 
would  be  generated  so  rapidly  that  steam  would  be  formed  and  both 
water  and  acid  would  be  thrown  violently  out  of  the  vessel,  burning 
whatever  it  came  in  contact  with. 

In  order  to  mix  the  water  and  acid  in  exactly  the  right  proportions 
an  instrument  called  a  hydrometer  is  used.  This  consists  of  a  glass 
tube  weighted  with  mercury  at  the  lower  end,  and  having  graduations 
marked  on  the  stem.  This  instrument  indicates  the  weight  or  density 
of  a  liquid  as  compared  with  pure  water.  It  is  used  by  allowing  it 
to  float  in  the  liquid  to  be  tested.  If  floated  in  rain  water  at  a  tem- 
perature of  4°  C,  it  will  sink,  to  a  point  marked  1.000  on  the 
stem.  If'  floated  in  a  liquid  heavier  than  water  it  will  not  sink 
so  far  and  the  mark  on  the  stem  will  be  greater  than  unity. 


52  GASOLOGY. 

In  making  up  the  electrolyte  for  storage  batteries  the  acid  should 
be  added  until  the  density  shows  1.200.     If  the  density  of  the  elec- 

. ,  -T.  trolyte    drawn    from 

W/res  I  a  cell  tests  less  than 

1.200  acid  should  be 
added,  if  more,  then 
add  water.  An  elec- 
trolyte of  higher 
density  will  make 


L*ws666  667  the  cel1  more  active< 

I  a~»,.L*r  but   it  wm   cauge   the 

|lliB£/.£Hy  cel1   to   Deteriorate 

_-|IIH»-£--  more   rapidly.      The 

-pIQ  -^g  electrolyte  should  be 

tested  frequently. 

A  storage  battery  may  be  tested  by  testing  each  cell  separately 
with  a  voltmeter.  An  ammeter  is  of  no  use  in  testing  storage  bat- 
tery cells,  although  it  is  the  correct  instrument  to  use  for  testing 
either  dry  or  wet  primary  cells.  When  the  voltage  of  the  storage 
battery  cells  drops  to  1.8  volts  per  cell  it  is  time  to  recharge. 

The  electrolyte  should  cover  the  plates  to  a  depth  of  about  one- 
fourth  inch.  If  some  of  the  electrolyte  is  spilled  add  some  of  the 
fresh  solution,  which  may  be  kept  at  hand  in  a  bottle  for  this  pur- 
pose. If  some  of  the  liquid  is  lost  through  evaporation  add  rain 
water  or  distilled  water. 

The  Rating  of  Storage  Batteries. — The  capacity  of  a  storage  bat- 
tery is  rated  in  ampere  hours.  For  example,  a  ten  ampere  hour 
battery  is  capable  of  delivering  a  current  of  ten  amperes  for  one  hour, 
or  one  ampere  for  ten  hours.  The  rate  of  discharge  is  thus  seen  to  be 
variable,  depending  upon  the  work  the  battery  is  called  upon  to  do. 
A  storage  battery  is  able  to  supply  a  heavy  current  for  a  short  time 
or  a  smaller  current  for  a  longer  time. 

In  considering  storage  batteries  for  electric  lighting,  it  is  cus- 
tomary to  multiply  the  ampere  hour  capacity  by  two  to  find  the 
number  of  16-candle  power  lamps  that  the  battery  is  able  to  carry 
for  one  hour.  Each  carbon  filament  16-candle  power  lamp  requires 
about  one-half  an  ampere  of  current,  so  that  one  ampere  per  hour  is 
sufficient  for  two  lamps.  A  ten  ampere  hour  battery,  therefore,  will 
run  twenty  lamps  one  hour  or  four  lamps  for  five  hours. 

Charging  from  a  Lighting  Circuit. — A  convenient  means  of  charg- 
ing storage  batteries  is  found  in  the  ordinary  incandescent  lighting 
circuits.  If  the  current  is  alternating,  a  rectifier  must  be  used  which 


STORAGE  BATTERIES.  5q 

will  change  it  to  direct  current,  for  only  direct  current  can  be  used 
in  charging  the  battery.  Where  direct  current  at  110  or  220  volts  is 
available,  lamps  may  be  used  for  resistance  if  a  suitable  rheostat  is 
not  at  hand. 

Figure  19  shows  the  method  of  wiring  where  lamps  are  used. 

A  bank  of  lamps  I,  connected  in  parallel,  is  connected  in  series  with 
the  battery.  A  double  pole  switch  s,  connects  the  battery  with  the 
service  wires  and  an  ammeter  is  placed  in  the  line  at  a.  This  in- 
strument is  not  absolutely  essential,  but  it  is  well  to  have  it  in  order 
to  be  certain  of  the  strength  of  the  charging  current.  The 
number  of  lamps  used  will  depend  upon  how  much  current  they 
require  and  the  charging  rate  of  the  battery.  This  latter  quantity 
may  be  determined  by  dividing  the  ampere  hour  capacity  of  the  bat- 
tery by  eight.  For  example,  if  the  battery  is  rated  at  forty  ampere 
hours,  it  will  take  a  five  ampere  current  to  charge  it.  If  the  line  pres- 
sure is  from  110  to  120  volts,  then  five  32-candle  power  lamps,  each 
requiring  a  current  of  one  ampere  must  be  used.  If  16-candle  power 
lamps  at  one-half  ampere  each  are  used,  it  will  require  ten  lamps. 
Fewer  lamps  can  be  used,  but  it  will  require  a  longer  time  to  charge 
the  battery. 

Laying  up  a  Battery. — If  a  battery  is  not  to  be  used  for  some  time 
it  may  be  kept  in  condition  by  giving  it  a  small  freshening  charge 
occasionally,  say  once  in  two  weeks.  This  charge  should  be  given 
at  a  very  slow  rate.  Where  the  battery  must  lie  idle  for  an  extended 
period,  as  it  frequently  does  in  many  summer  or  winter  resorts,  it 
should  be  put  in  dry  storage.  To  do  this  proceed  as  follows :  —  First 
charge  the  battery  at  normal  rate  until  it  is  completely  charged,  then 
syphon  out  the  electrolyte  and  place  in  clean  bottles  for  use  when 
the  battery  is  to  be  recharged.  As  each  cell  is  emptied,  refill  it 
immediately  with  pure  cold  water.  After  all  the  cells  have  been 
treated  in  this  manner,  connect  up  the  battery  and  discharge  it  until 
the  voltage  falls  to  one  volt  per  cell.  When  this  point  has  been 
reached  the  water  should  be  drawn  off.  If  the  battery  gets  hot  dur- 
ing discharge  add  cold  water  to  take  up  the  excess  heat.  After  being 
emptied  of  water  the  battery  may  stand  for  an  indefinite  period  with- 
out suffering  any  injury. 


Statio 


CHAPTER  VI 
WIRING  AN  ENGINE 

LESSON  XVI. 

This  is  a  subject  that  gives  probably  as  much  trouble  as 
any  other  feature  of  gas  engine  operation,  and  it  is  proposed  in  this 
and  succeeding  lessons  to  present  a  few  wiring  diagrams  with  the 
purpose  in  view  of  acquainting  our  readers  with  the  principles,  at 
least,  of  this  subject 

All  wire  used  should  be  preferably  rubber  insulated.  Cotton  insu- 
lated wire  is  not 
nearly  as  satisfac- 
tory, first,  because 
the  insulation  soon 
becomes  worn  in 
service;  and  second, 
because  the  cotton 
absorbs  more  or  less 
moisture.  Wire  of 
proper  size  should  FIG.  20. 

be  used  since  very  small  wire  presents  too  much  resistance  to  the 
flow  of  current,  especially  if  the  external  circuit  be  long. 

All  joints  should  be  scraped  clean  and  all  binding,  nuts  and  screws 
should  be  set  up  tightly  with  a  pair  of  pliers.  Wherever  there  is  a 

loose  connection 
there  will  form  an 
oxide  of  copper, 
which  is  a  good  in- 
sulator, and  even  if 
current  does  pass 
through  it  will  be 
weaker  on  account 


Cttrn 


corjnecteB  j 
FIG.  21. 


of  the  resistance  at 
that  point.  All  wires  should  be  supported  and  not  be  allowed  to  hang 
or  flop.  A  loose  wire  is  apt  to  rub  against  some  metal  part  of  the 
engine  and  cause  a  short  circuit  at  that  part,  thus  stopping  the  engine 
and  perhaps  ruining  the  battery. 

The  simplest  style  of  wiring  is  for  a  single  cylinder  engine  fitted 
with  make  and  break  igniter.     This  is  illustrated  in  figure  20.     The 


WIRING  AN  ENGINE.  55 

battery  consisting  of  four  cells  is  connected  in  series,  that  is,  one 
cell  behind  the  other  with  the  carbon  of  one  cell  joined  to  the  zinc 
of  the  next,  and  so  on.  When  the  cam,  which  revolves  at  half  the 
engine  shaft  speed,  forces  the  movable  electrode  into  contact  with 
the  stationary  electrode,  the  circuit  is  completed  and  current  flows 
from  one  electrode  to  the  other.  When  the  cam  passes  the  movable 
electrode  the  current  is  broken  and  a  spark  is  formed  at  the  break. 
No  more  current  can  be  used  until  the  electrodes  are  again  in  contact. 
Where  from  four  to  six  cells  are  used  in  one  battery  they  are 
always  connected  in  series  since  this  arrangement  gives  the  greatest 
voltage.  For  other  kinds  of  work  other  styles  of  connection  are 
sometimes  adopted,  as  shown  in  figures  21  and  22.  The  former  rep- 
resents what  is  called  connecting  cells  in  multiple  and  the  latter 
multiple  series.  The  voltage  and  amperage  differ  in  the  different 
styles  of  connec- 
tions. For  example: 
If  N  represents  the 
number  of  cells;  V, 
the  voltage  of  one 
cell;  and  A,  the  am- 
will  be  N  times  V; 
perage  of  one  cell, 
then  the  voltage  of 


-,  .  .  _//  t.tni  «./  f  •  \^  —  S&T'/ti'S 

a    battery   in   series  ._ 

if  connected  in  mul- 
tiple, V;  and  in  multiple  series  S  times  V,  where  S  represents  the 
number  of  series  units.  The  amperage  will  be  for  series  connection 
A,  for  multiple  N  times  A,  and  for  multiple  series  S  times  A.  To 
illustrate:  If  the  amperage  of  each  cell  shown  is  20  and  its  voltage 
1,  then  in  figure  20  the  battery  will  show  four  volts  and  twenty  am- 
peres. In  figure  21  there  will  be  one  volt  and  one  hundred  amperes, 
while  figure  22  will  record  two  volts  and  forty  amperes.  In  other 
words,  we  will  obtain  the  largest  flow  of  current  from  figure  21  and 
the  least  current,  but  greatest  voltage  from  figure  20. 

Series  connection  adds  all  the  voltages  together,  while  multiple 
connection  adds  the  amperage  of  each  cell.  It  has  the  effect  of  form- 
ing a  single  cell  whose  carbons  are  the  sum  of  all  the  carbons  and 
its  zinc  the  sum  of  all  the  zincs  in  the  individual  cells.  In  this 
discussion  no  account  has  been  taken  of  resistances  of  either  the 
internal  or  external  circuits. 

The  Timer. — Where  there  are  two  or  more  cylinders  to  be  ignited 
from  a  single  battery  or  other  source  of  current,  it  is  necessary  to 


56 


GASOLOGY. 


provide  what  is  called  a  timer  or  commutator,  which  will  connect 
the  battery  first  to  one  cylinder  and  then  to  another  in  the  proper 
order  of  their  ignition.  Such  a  device  is  nothing  more  than  a  re- 
volving switch  actuated  by  the  engine  itself  from  gearing  attached 
to  the  crank  shaft.  A  crude  form  of  timer  illustrating  the  principle 
of  all  timers  appears  in  figure  23.  It  consists  of  a  fibre  ring,  usually 
enclosed  in  a  metal  case  having  a  cam  shaft  passing  up  through  its 
center.  This  shaft  carries  a  block  with  an  arm  on  the  end  of  which 

is  a  contact  wheel. 
The  wheel  is  pressed 
outward  by  a  com- 
pression spring.  As 
the  shaft  revolves, 
it  carries  the  con- 
tact wheel  around 
and  makes  contact 
with .  the  various 
binding  posts 
through  the  metal 
segments  whose  in- 
ner faces  are  flush 
with  the  fibre  ring. 


Shaft 


Con*«c* 


Time*  for    -*-cy7/Wer  Engine. 
FIG.  23. 


Whenever  the  con- 
tact wheel  touches  one  of  these  metal  contact  pieces,  current  can 
flow  through  the  contact  wheel,  the  arm  that  carries  it  and  the  cam 
shaft  to  the  engine  frame  from  which  it  can  pass  back  through  the 
grounded  connection  to  its  source. 

In  this  connection  it  may  be  well  to  state  that  a  ground  connection 
means  a  connection  to  the  engine  frame,  but  not  necessarily  to  the 
earth.  The  timer  housing  is  provided  with  a  lever  connection  where- 
by it  may  be  rotated  several  degrees  and  thus  change  the  time  of 
contact  with  reference  to  the  engine  shaft  while  the  engine  is  run- 
ning. Timers  are  made  with  one,  two,  three,  four,  or  more  binding 
posts  for  engines  having  a  like  number  of  cylinders. 

In  all  problems  of  wiring  there  is  one  fundamental  fact  that  must 
be  borne  in  mind  continually,  and  that  is,  each  circuit  must  ~be  com- 
plete in  order  to  get  a  current  through.  Here  is  where  a  lot  of  people 
have  trouble.  They  do  not  make  certain  that  each  circuit  is  complete 
before  taking  up  the  next.  If  they  did  they  would  have  less  difficulty 
in  laying  their  wires.  This  is  not  as  simple  as  it  might  seem  when 
one  has  several  separate  sources  of  current  with  multiple  switches  and 
perhaps  jump  spark  ignition. 


WIRING  AN  ENGINE. 


57 


Since  jump  spark  ignition  presents  some  difficulty  to  many  people 
we  have  prepared  a  diagram,  figure  24,  to  illustrate  one  of  the  funda- 
mental features  of 
this  form  of  igni- 
tion. The  point  we 
wanted  to  illustrate 
is  the  one  just  men- 
tioned, that  is,  that 
the  various  circuits 
must  be  complete. 
In  this  diagram 
there  are  two  cir- 
cuits, the  primary 
marked  P,  and  the 
secondary  marked 
S.  There  are  only 
three  wires  to  the 
engine  from  the 
coil,  and  this  is 
what  causes  trouble. 

There  are  two 
distinct  circuits  in 
the  coil — the  prim- 
ary from  the  bat- 
tery, consisting  of 
coarse  wire,  and 
outside  of  this  and 


T/rrrer  _ 


FIG.  24. 


insulated  from  it  a  fine  coil  of  wire  called  the  secondary.    When  the 

current  flows 
through  the  primary, 
an  induced  current 
flows  through  the 
secondary  and 
jumps  the  gap  in 
the  spark  plug.  By 
referring  to  the  dia- 
gram it  will  be  seen 
that  the  timer  closes 
the  primary  circuit, 
using  the  engine  as 
a  part  Of  the  circuit. 


25. 


When  this  occurs  the  secondary  current  flows  through  the  spark  plug, 


58 


GASOLOGY. 


jumps  to  the  engine  frame  and  goes  back  to  the  coil  through  the 
common  ground  wire  and  thus  completes  the  circuit.  It  would  be 
possible  and  perhaps  less  confusing  to  use  two  ground  wires,  one  for 
the  primary  and  the  other  for  the  secondary — thus  making  four 
binding  posts  on  the  coil  box. 

LESSON  XVII. 

Figure  26  illustrates  the  method  of  connecting  jump  spark  ignition 
to  a  two-cylinder  engine  whose  cranks  are  set  180  degrees  apart.    Two 
batteries  are  used  and  two  coils.    Either  battery  may  be  switched  in 
by  means  of  a  two  point  switch  on  the  coil  box.     The  secondary  cir- 
cuit    is     completed 
through   the  engine 
frame,    the   vertical 
shaft   of  the  timer, 
and      the      primary 
connection    back    to 
the  spark  coil  where 
'<?>   connection   is   made 
to      the      secondary 
*   winding    after    the 
manner     shown     in 
figure  24  in  the  pre- 
ceding lesson. 

In    figure    27    a 


TH/O  cxt//yz?£>?.$  - 


FIG.  26. 


method  is  shown  for  connecting  both  dry  batteries  and  storage  bat- 
teries so  that  either  may  be  used  as  desired.  The  same  ground  wire 
is  used  for  both  the  dry  and  storage  batteries  as  are  also  the  same 
coil  and  timer.  The  two  point  switch  is  placed  on  the  side  of  the 
coil  box. 

It  is  customary  on  the  best  cars  at  the  present  time  to  use  a 
separate  coil  for  each  cylinder.  This  makes  it  easier  to  locate  trouble, 
when  it  occurs,  with  the  ignition.  The  connections  on  the  different 
coils  can  be  changed  and  if  the  trouble  still  continues  it  shows  that 
the  difficulty  is  not  in  the  coils,  but  if  the  trouble  remains  at  the 
same  coil  when  connected  to  a  different  cylinder,  the  trouble  will  be 
generally  found  in  the  coil. 

Figure  28  shows  a  four-cylinder  engine  connected  up  with  four 
coils,  the  current  being  supplied  by  a  battery.  In  wiring  a  multi- 
cylinder  engine  each  circuit  should  be  completed  and  tested  before 


WIRING  AN  ENGINE. 


59 


another  one  is  started.  In  this  way  all  danger  of  confusing  the 
circuits  is  obviated.  The  primary  wire  should  first  be  laid  from  its 
coil  unit  to  the  ap- 
propriate timer  con- 
tact. When  the 
switch  is  closed  the  .  xPnmaru 
vibrator  of  the  coil 
will  buzz  when  the 
timer  contact  piece 
makes  connection 
with  the  segment  to 
which  the  wire  is  at- 
tached. A  buzzing 
of  the  vibrator  when 
the  switch  is  open 
indicates  a  short  cir- 
cuit somewhere.  The 
secondary  wire 
should  now  be  put 
down  before  at- 
tempting the  next 
primary  circuit. 
This  should  be  test- 


FIG.  27. 


ed  by  noting  if  a  spark  appears  at  the  spark  plug,  which  latter  may 
be  unscrewed  and  placed  with  its  shell  in  contact  with  the  engine 

frame  so  that  the 
spark  may  be  ob- 
served. When  the 
spark  lever  is  fully 
f  retarded  the  spark 
should  appear  when 
the  piston  reaches 
the  dead  center  on 
its  compression 
stroke. 

The  timer  contacts 
for  a  four  -  cylinder 
engine  must  be  ar- 


°°' 


ranged  with  reference  to  the  firing  order  of  the  different  cylinders, 
which  in  turn  is  established  by  the  order  of  opening  of  the  exhaust 
valves.  Suppose  this  order  is  1,  2,  4,  3,  as  in  figure  28.  After  the  first 
cylinder  is  connected  up  in  the  manner  just  described,  the  next'  one 
to  be  wired  is  number  two,  and  the  primary  wire  should  be  connected 


60 


GASOLOGY. 


to  the  next  timer  contact  in  the  direction  of  rotation  of  the  timer. 
The  primary  of  coil  number  four  should  be  attached  to  the  next  bind- 
ing post  of  the  timer  and  the  corresponding  secondary  run  to 
cylinder  number  four.  The  remaining  coil,  timer  contact,  and 
cylinder  should  now  be  connected  up,  thus  completing  the  wiring. 
The  direction  of  rotation  of  the  timer  is  indicated  by  the  arrow. 

Where  only  a  single  coil  is  used  on  a  multiple  cylinder  engine  it  is 
necessary  to  use  a  timer  and  a  secondary  distributor.  A  diagram  rep- 
resenting this  style  of  connection  appears  in  figure  29.  For  con- 
venience in  showing  the  connections  the  primary  timer  and  the  dis- 
tributor are  separated,  although  this  is  not  customary  in  practice. 
Usually  both  are  connected  together,  one  side  being  for  the  dis- 
tributor and  the  other  side  for  the  timer.  Only  one  source  of  cur- 
rent is  shown  in  the 
drawing,  but  there 
*tor  is  nothing  to  pre- 
vent wiring  in  such 
a  way  as  to  be  able 
to  use  two  or  more 
sources  of  current. 
This  style  of  igni- 
tion is  not  used  as 
much  as  it  has  been 
in  former  years. 
The  advantages  of 
the  multiple  coil 
system  indicate 
some  of  the  disad- 


FIG.  29. 


vantages  of  this  type.  It  has,  however,  some  positive  advantages, 
such  as  reducing  the  number  of  connections,  and  making  only  one 
coil  to  adjust. 

In  our  next  lesson  we  will  show  different  methods  of 'wiring  en- 
gines for  magneto  ignition. 


LESSON  XVIII. 

There  are  two  principal  methods  by  which  ignition  in  a  gas  engine 
cylinder  may  be  accomplished,  using  a  magneto.  The  first  is  with 
a  low  tension  magneto  adapted  to  the  make  and  break  system  of  igni- 
tion, and  the  second  with  a  high  tension  magneto  adapted  to  the 
jump  spark  system.  There  are  many  modifications  of  the  latter 
system,  some  of  which  will  be  discussed  in  succeeding  lessons.  In 


WIRING  AN  ENGINE. 


61 


this  lesson  we  will  consider  first  the  low  tension  system  using  make 
and  break  ignition.  In  this  type  of  ignition  the  igniter  is  just 
the  same  as  for  battery  ignition.  There  is  one  stationary  electrode 
and  one  movable.  The  movable  electrode  is  brought  into  contact 
with  the  stationary  or  insulated  electrode  at  the  proper  time  in  the 
stroke  by  the  action  of  a  cam  acting  on  a  tappet.  The  current  from 
the  magneto  flows  from  the  magneto  through  the  contact  points, 
thence  to  the  engine  frame  and  then  to  the  magneto,  completing  the 
circuit. 


FIG  30. 

At  the  right  time  in  the  stroke  the  two  contact  points  are  quickly 
separated  and  an  arc  is  formed  in  consequence,  thus  igniting  the 
charge.  This  action  is  in  nowise  different  from  what  obtains  when 
a  battery  is  used  except  that  it  is  not  necessary  to  use  a  spark  coil,  as 
the  voltage  and  strength  of  current  of  the  magneto  are  sufficient  with- 
out any  intensification  with  a  coil.  The  method  of  wiring  is  therefore 
very  simple.  All  that  is  needed  is  a  wire  from  the  magneto  ground- 
ed on  the  engine  frame  by  having  its  base  attached  thereto  so  that 
the  circuit  is  complete  when  the  two  contact  points  are  together. 

When  several  cylinders  are  fired  with  the  same  magneto  it  is  cus- 
tomary to  use  what  is  called  a  bus  bar,  that  is,  a  common  wire  from 
the  magneto,  to  which  all  the  individual  wires  are  attached. 

When  it  is  desired  to  stop  the  engine  the  magneto  is  short  cir- 
cuited on  itself  by  means  of  a  switch  between  the  bus  bar  and  the 


62 


GASOLOGY. 


engine  frame.  This  causes  the  current  to  go  back  through  the  en- 
gine frame  to  the  magneto.  It  would  be  possible  to  stop  the  engine 
by  simply  opening  the  switch  leading  to  the  various  cylinders  and 
not  causing  the  current  to  go  back  to  the  magneto,  but  this  might 
result  in  injury  to  the  magneto,  since  the  current  which  it  would 
continue  to  generate  would  have  no  outlet  and  might  break  through 
the  insulation  of  its  own  windings,  causing  permanent  injury. 

It  must  be  remembered    in  considering  magneto  ignition  that  the 
armature  of  the  magneto  must  occupy  a  certain  position  with  refer- 


neto 


FIG.  31. 

ence  to  the  field  magnets  at  the  instant  ignition  occurs  (see  figure  30), 
as  the  current  generated  by  the  magneto  when  in  any  other  position  is 
very  feeble.  For  a  magneto  whose  armature  rotates,  it  is  necessary, 
therefore,  that  it  revolve  at  a  certain  speed,  relative  to  that  of  the 
crank  shaft,  so  that  it  will  occupy  the  position  shown  in  the  figure 
when  ignition  occurs.  It  is  furthermore  necessary  that  the  time  of 
ignition  be  fixed  absolutely  with  reference  to  the  speed  of  the  en- 
gine and  this  makes  some  sort  of  positive  drive  necessary.  The 
usual  method  of  obtaining  this  is  by  means  of  a  gear  on  the  crank 
shaft  driving  one  having  the  requisite  number  of  teeth  on  the  arma- 
ture shaft.  A  belt  or  friction  drive  is  not  suitable  because  of  slip- 
page and  the  consequent  getting  out  of  time  of  the  magneto. 

The  correct  time  for  ignition  to  occur  is  during  the  compression 
stroke,    shortly   before   the    piston    reaches    dead   center.     On    most 


WIRING  AN  ENGINE. 


63 


automobiles,-  and,  in  fact,  other  engines  as  well,  the  piston  is  given 
a  lead  of  about  one-half  an  inch,  that  is,  ignition  occurs  when  the 
piston  is  from  one-half  to  three-quarters  of  an  inch  from  the  end 
of  the  stroke.  The  correct  timing  of  the  ignition,  therefore,  con- 
sists in  causing  it  to  occur  at  this  point.  This  may  be  accomplished 
by  measuring  down  from  the  top  of  the  cylinder  to  the  piston  and 
then  adjusting  the  gears  so  as  to  bring  the  armature  into  the  po- 
sition shown  in  figure  30  at  that  time. 


Two-Point 


tv/t-h  Co/ 7. 


FIG.  32. 

Figure  31  is  a  diagrammatic  sketch  showing  the  method  of  wir- 
ing switches,  etc.,  for  a  low  tension  magneto.  With  the  above  de- 
scription no  other  explanation  should  be  needed  to  make  the  system 
perfectly  plain. 

Figure  32  shows  how  an  engine  may  be  connected  up  with  a  low 
tension  magneto  using  a  dry  battery  and  coil  to  start  with.  After 
the  engine  comes  up  to  speed  the  two  point  switch  may  be  thrown 
over,  cutting  out  the  battery  and  cutting  in  the  magneto.  This  is 
the  common  method  of  connecting  a  system  of  this  kind,  as  it  is 
necessary  to  bring  the  magneto  of  this  type  up  to  a  higher  speed 
than  can  conveniently  be  done  by  hand  cranking,  in  order  for  it  to 
generate  sufficient  current  for  ignition. 


VO.OFCYL. 


CHAPTER  VII 

ENGINE  BALANCE 

LESSON  XIX. 

One  of  the  difficulties  encountered  in  designing  and  constructing 
all  reciprocating  engines,  whether  they  be  driven  by  steam  or  gas 

power,  is  to  secure  steady,  even  motion 
1  and  prevent,  so  far  as  possible,  excessive 

.        ||  vibration. 

The  reason  for  vibration  in  all  such 

.  I  J  engines  arises  from  the  fact  that  all  re- 

-*         L  ciprocating  parts,  such  as  the  piston  and 

connecting  rod,  are  obliged  to  come  to 
ri  rest  twice  during  every  revolution,  and 

•  '  twice  be  brought  up  to  maximum  speed. 

In  addition  to  this  we  also  encounter  the 
condition  of  a  very  variable  driving  force 
acting  at  intervals  only,  in  the  case  of 
the  gas  engine.  This  complicates  the 
problem  considerably  and  has  required 
the  exercise  of  the  very  best  engineering 
skill  to  overcome.  Even  with  all  the  thought  and  study  and  skill 
with  which  this  problem  has  been  approached  it  is  not  completely 
solved  and  never  can  be,  owing  to  the 
variable  and  intermittent  nature  of  the 
forces  involved.  However,  much  prog- 
ress has  been  made  in  the  past  few  years, 
thanks  to  the  severe  demands  made  by 
the  automobile  trade,  and  at  the  present 
time  engines  are  built  in  which  vibra- 
tion has  been  reduced  to  a  point  which 
is  not  particularly  objectionable.  Some 
of  the  means  through  which  this  has 
been  accomplished  will  be  explained  in 
this  lesson. 

Engines  having  only  one  cylinder 
may  be  balanced  to  some  extent  by  the 
judicious  use  of  counter  weights  placed 
either  directly  opposite  to  the  crank, 
or  else  placed  opposite  to  the  crank  in 
the  fly  wheels. 


FIG.  33. 


2 

-on 


FIG.  34. 


ENGINE  BALANCE. 


65 


C71ANKS  0*  SAME   <S/B£ 


\WO.OF 
,    CYL'iS 

OTtJJET?  OF  STROKES 

1 

•P 

& 

3 

c 

z 

s 

c 

;p 

& 

The  effect   of   these   counter   weights   is   to   set   up   an   oppositely 
acting  force   which   attains   its  maximum  value  at   the  instant  the 
piston  and  connecting  rod  come  to  rest.     Thus  one  force  acting  in 
one  direction   is  made  to  offset  another 
and  presumably   equal   force    acting   in 
the  opposite  direction.     The  result  is  a 
nullification   of  both   forces  and   conse- 
quent lack  of  vibration  of  the   engine 
frame.     To  this  condition  is  added  the 
steadying  effect  of  very  heavy  fly  wheels, 
which  serve  to  absorb  energy  during  the 
power  stroke  and  deliver  it  to  the  crank 
shaft  during  the  idle  strokes  of  the  en- 
gine.    A  perfect  or,  in  fact,  a  near  ap- 
proach to  perfect  absorption  of  vibration 
by  this  means  would  require  the  engine 
to  run  at  constant  speed,  since  a  change 
in  speed  changes   the   intensity   of  the 
centrifugal  forces  set  up  by  the  revolv- 
ing weights   in   a   different   ratio   from  FIG.  35. 
the  way  in  which  the  forces  due  to  the  reciprocating  forces  change. 
Consequently,  an  engine  of  this  type  can  be  balanced  correctly  for 

only  one  speed,  and  will  vibrate  more 
and  more  as  the  speed  varies  from  the 
standard. 

The  difficulty  inherent  in  the  single 
cylinder  engine  has  led  to  the  general 
adoption  of  engines  having  two  or  more 
cylinders.  In  multiple  cylinder  engines, 
as  they  are  called,  the  pistons  and  re- 
ciprocating parts  can  be  so  arranged 
that  they  move  in  opposite  directions, 
and,  if  care  is  taken  to  make  these  parts 
of  equal  weight,  they  will  counterbalance 
each  other  at  any  speed  and  thus  reduce 
vibration  to  a  very  small  amount. 

This  is  the  plan  adopted  in  all  double 
opposed  engines  of  the  horizontal  type, 
and  is  found  to  be  quite  satisfactory  for 
all  low  powered  engines.  The  pistons 


FIG.    36. 


are  placed  horizontally  on  each  side  of  the  crank  shaft,  with  their 
open  ends  opposite  each  other.     The  cranks  are  placed  180  degrees 


66 


GASOLOGY. 


i  Z  3  4- 

RRRFR 


apart,  or,  in  other  words,  on  exactly  opposite  sides  of  the  crank  shaft. 
Thus  both  pistons  reach  the  head  ends  of  their  respective  cylinders 
at  the  same  instant,  but  travel  in  opposite  directions  to  do  so.  Thus 
the  shock  occasioned  by  bringing  one  piston  to  rest  is  offset  by  the 
other. 

The  order  of  the  different  events  of  the  strokes  is  tabulated  in 
Fig.  34.  In  this  table  P  represents  the  power  stroke;  E  exhaust;  S 
suction  and  C  compression.  An  outward  stroke  must  be  either  a 
power  stroke  or  a  suction  stroke,  and  an  inward  stroke  either  exhaust 
or  compression.  It  will  be  observed  that  with  this  arrangement  of 
cylinders  a  power  stroke  can  be  made  to  occur  during  each  revo- 
lution, if  the  valves  and  cams  are  set  right.  The  upper  set  of 
events  opposite  2  in  the  figure  shows  the  correct  arrangement,  while 

the  lower  set  of  events  shows  a  faulty 
arrangement,  since  it  brings  both  power 
strokes  in  the  same  revolution. 

Two-cylinder  engines  are  often  placed 
side  by  side,  as  indicated  in  Figs.  35  and 
36.  Two  arrangements  of  the  cranks  are 
possible  with  this  construction.  They 
may  be  placed  opposite,  or  180  degrees 
apart,  or  on  the  same  side  of  the  shaft, 
in  which  case  they  are  said  to  be  360 
degrees  apart.  The  order  of  strokes  for 
both  cases  is  clearly  indicated  in  the 
figures.  In  Fig.  35,  there  is  a  power 
stroke  once  in  each  revolution.  The 
table  shows  an  idle  stroke  in  each  cylin- 
der between  the  power  strokes,  but  in 
Fig.  36  both  power  strokes  occur  in  a 
single  revolution,  while  the  other  revo- 
lution is  idle  during  both  strokes  in  the 
two  cylinders. 

In  the  arrangement  shown  in  Fig.  35,  the  reciprocating  forces  are 
not  balanced,  while  in  Fig.  36  they  are.  However,  of  the  two,  the 
former  is  preferable,  since. it  gives  a  steadier  motion  to  the  crank 
shaft  and  counter  weights  may  be  used  to  offset  the  unbalanced 
forces  due  to  the  reciprocating  parts. 

Of  the  three  arrangements  of  the  two  cylinders,  the  horizontal 
double  opposed  possesses  greater  advantages  and  is  the  preferable 
one  to  use. 


UJ 


HO.  OF  CYLS 

onotn  of  sr/ro*£.s 

1 

IP 

E 

xS 

C 

2 

& 

^ 

C 

^ 

3 

C 

P, 

&  / 

£ 

4- 

3 

C 

y 

Z 

FIG.  37. 


ENGINE  BALANCE.  67 

In  Fig.  37  there  is  shown  a  sketch  of  a  four-cylinder  vertical 
engine  such  as  is  generally  used.  The  two  end  cranks  point  in  one 
direction  and  the  two  middle  ones  in  the  opposite  direction,  being 
thus  arranged  in  pairs  180  degrees  apart.  The  table  shows  the  order 
of  the  strokes  in  each  cylinder.  An  inspection  of  the  figure  will 
show  that  the  order  of  firing  is  1,  3,  4,  2.  Nearly  all  engines  of  this 
type  are  timed  to  fire  in  this  way. 

A  further  discussion  of  the  four-cylinder  engine  will  be  taken  up 
in  the  next  lesson. 

LESSON  XX. 

Some  of  the  difficulties  of  securing  a  perfectly  balanced  engine 
were  pointed  out  in  the  last  lesson  and  will  be  considered  at  greater 
length  in  the  present  lesson. 

There  are  two  classes  of  forces  that  produce  vibration;  those  due 
to  reciprocating  masses  and  those  due  to  rotating  masses.  The 
former  may  be  perfectly  balanced  by  similar  masses  acting  in  the 
opposite  direction  at  exactly  the  same  instant  and  in  the  same  line 
of  action.  For  example,  the  forces  set  up  by  the  piston  and  other 
reciprocating  parts  of  one  cylinder  of.  a  double  opposed  engine  may 
be  exactly  balanced  by  similar  parts  of  the  other  engine,  provided 
both  cylinders  are  exactly  opposite;  that  is,  if  the  same  center  line 
passes  through  both  cylinders.  If  this  condition  does  not  exist 
there  will  be  what  is  called  a  force  couple  acting  which  will  tend  to 
rotate  the  cylinder  in  a  horizontal  plane  if  they  are  placed  horizon- 
tally. 

The  only  way  to  have  the  cylinders  exactly  opposite  is  to  make 
the  connecting  rods  with  interlocking  ends,  both  acting  on  the  same 
crank  pin.  This,  however,  is  rarely  done  in  the  case  of  gas  engines, 
since  the  construction  of  the  double  opposed  engine  is  such  that  the 
distance  between  cranks  is  only  about  one-half  the  length  of  the 
crank  pin  and  the  lever  arm  of  the  couple  is  thus  quite  short. 
Where  vertical  two-cylinder  engines  are  used  this  lever  arm  is  much 
longer,  being  about  one  and  one-half  times  the  length  of  the  crank 
pin,  owing  to  the  double  cylinder  walls  and  double  water  jacket  be- 
tween cylinders. 

A  four-cylinder  engine  having  the  two  outer  cylinders  arranged  as 
a  pair  and  opposed  to  the  two  inner  ones,  is  perfectly  balanced  so 
far  as  the  reciprocating  forces  only  are  concerned.  One  pair  of 
pistons  moves  in  one  direction  and  the  other  pair  moves  in  the  op- 
posite direction.  If  care  is  taken  to  make  all  the  pistons  and  con- 
necting rods  of  equal  weight,  very  good  results  may  be  obtained.  In 


68  GASOLOGY. 

the  best  automobile  factories  great  care  is  taken  in  this  particular, 
it  being  the  practice  to  reduce  all  reciprocating  parts  of  the  various 
cylinders  to  the  same  weight  within  a  fraction  of  an  ounce.  This 
practice  results  in  the  minimum  of  vibration  and  is  necessary  for 
high  speed  automobile  engines  and  boat  engines. 

There  are,  however,  some  unbalanced  forces  even  if  the  weights 
of  reciprocating  parts  are  exactly  the  same.  These  arise  from  the 
rotation  of  the  crank  and  the  oscillation  of  the  free  end  of  the  con- 
necting rod.  These  forces  cause  some  vibration,  but  they  can  not  be 
perfectly  balanced  unless  use  is  made  of  other  rotating  parts  of 
equal  weight  and  similarly  placed,  revolving  in  an  opposite  direc- 
tion. This  remedy  would  lead  to  a  complication  of  parts  and  the 
benefits  to  be  derived  being  small,  at  best,  it  is  not  generally  thought 
wise  to  make  use  of  it. 

In  four-cylinder  engines,  it  was  shown  in  the  last  lesson,  the 
order  of  firing  of  the  cylinders  might  be  1,  2,  4,  3;  or  1,  3,  4,  2.  The 
first  engines  built  were  all  arranged  to  fire  in  the  order  first  given,  but 
a  little  consideration  will  show  that  the  latter  order  will  give  better 
results,  since  the  force  .of  the  explosion  is  distributed  over  the  en- 
gine to  better  advantage.  This  is  the  order  that  is  being  generally 
adopted  at  the  present  time. 

Three-cylinder  engines  are  arranged  with  the  cranks  set  120  de- 
grees apart  instead  of  180  degrees,  as  is  the  case  with  double  op- 
-T.  1  posed  or  four-cylin- 

C-  Z*M/7/l     -*  i  •  mi    • 

der  engines.  Ihis 
arrangement  results 
in  excellent  balance 
of  the  reciprocating 
parts  and  in  excel- 
lent turning  effort  at 
*t  the  crank  shaft. 

The    stresses    due 

Crtf^-f^l^v^         ^4Sf  to  the  explosion  of 

the  charge  are  very 
evenly      distributed 

5^  since  there  are  two 

-pIG   gg  power    strokes    dur- 

ing two  revolutions 

of  the  crank.  While  the  crank  is  making  two  complete  turns,  or 
720  degrees  of  rotation,  power  is  applied  through  three  half  revo- 
lutions, or  a  total  of  540  degrees.  The  longest  period,  with  this  ar- 
rangement, between  the  end  of  one  power  stroke  and  the  begin- 


ENGINE  BALANCE.  69 

ning  of  the  next,  is  while  the  crank  is  passing  through  an  angle  of 
60  degrees.  This  fact  is  clearly  brought  out  in  the  accompanying 
drawing,  Fig.  38.  Six-cylinder  engines  have  crank  shafts  of  sim- 
ilar construction  to  three-cylinder  engines,  with  the  cranks  arranged 
in  pairs.  This  arrangement  gives  six  power  strokes  in  two  revolutions 
and  provides  the  best  torque  and  best  balance  obtainable  without  us- 
ing an  excessive  number  of  cylinders.  In  fact,  very  little  additional 
benefit  would  be  obtained  by  using  as  high  as  twelve  cylinders; 
while  the  complication  of  parts  and  difficulty  in  keeping  in  repair 
would  be  enormously  increased. 

It  would,  therefore,  appear  from  the  foregoing  discussion  that 
for  small  runabouts  and  light  powered  machines,  especially  those  of 
the  high-wheeled  type,  the  double  opposed  motor  has  many  ad- 
vantages. It  is  cheap,  easy  to  take  care  of,  is  not  complicated,  and 
has  fairly  good  torque  and  good  balance.  The  four-cylinder  verti- 
cal engine  is  better  than  the  double-opposed,  but  is  more  complicated, 
costs  more,  and  is  particularly  adapted  to  high  grade  cars,  especially 
touring  cars  and  cars  of  large  power.  The  six-cylinder  motor  rep- 
resents about  the  highest  grade  of  present  day  gas  engine  construc- 
tion, but  it  is  expensive,  complicated  and  difficult  for  the  ordinary, 
unskilled  individual  to  manage.  It  is  adapted,  therefore,  to  the 
expensive,  high  grade  cars,  managed  by  skilled  attendants.  It  prob- 
ably will  never  be  used  to  any  extent,  if  at  all,  for  farm  engine  pur- 
poses. The  one,  two  and  four-cylinder  engines  are  used  extensively 
for  farm  work  at  the  present  time;  the  one-cylinder  motor  for  all 
light  work,  such  as  sawing,  grinding,  pumping,  etc. ;  the  two-cylinder 
and  four-cylinder  motors  for  automobiles  and  farm  tractors.  There 
are  also  some  quite  successful  farm  tractors  of  the  one-cylinder 
type. 

All  single  cylinder  engines  depend  upon  a  heavy  fly  wheel  to 
preserve  steady  motion  and  to  a  certain  extent  prevent  vibration. 
In  general,  it  may  be  said  that  the  heavier  the  fly  wheel  the  less  the 
speed  of  the  engine  will  vary.  Consequently,  gas  engines  used  to 
run  electric  dynamos  must  be  fitted  with  very  heavy  fly  wheels 
or  the  speed  of  the  engine  will  vary  enough  to  make  the  lights 
flicker  badly.  An  engine  designed  for  pumping  and  light  farm  work 
will  in  general  vary  too  much  in  speed  to  be  used  to  run  a  dynamo. 
If,  however,  it  be  fitted  with  an  extra  heavy  fly  wheel  it  will  usually 
prove  quite  satisfactory. 


CHAPTER  VIII 
CARBURETORS 

LESSON  XXL 

Neither  pure  liquid  gasoline  nor  pure  gasoline  vapor  will  burn 
in  a  closed  vessel.  An  engine  charged  with  gasoline  vapor  only  would 
not  run.  In  order  to  make  gasoline  vapor  inflammable  it  must  be 
mixed  with  the  right  amount  of  air  in  order  to  obtain  sufficient 
oxygen  for  combustion. 

The  mixing  of  the  air  and  gasoline  vapor  is  called  carburet  ion. 
That  is,  the  air  is  carburetted  or  charged  with  the  carbonaceous 
fuel.  The  apparatus  or  device  in  which  this  act  is  accomplished 
is  called  a  carburetor  or  sometimes  a  mixer.  The  former  name  is 
now  used  almost  exclusively  and  is  the  name  that  will  be  adhered  to 
in  these  lessons. 

In  searching  the  literature  of  gas  engines  very  little  data  was 
found  pertaining  to  mixtures  of  air  and  gasoline  and  apparently 
there  is  little  exact  information  available.  It  is  known  that  a  proper 
mixture  will  explode  readily  and  do  its  work  with  the  accompaniment 
of  very  little  smoke  at  the  exhaust  or  the  clogging  of  the  valves  with 
a  deposit  of  tar.  If  the  mixture  is  not  right  both  of  these  things  may 
occur  and  trouble  will  be  experienced  in  running  the  engine. 

Experience  indicates  that  only  very  slight  variations  are  per- 
missible in  the  mixture  in  order  even  to  make  the  engine  work  at  all. 
If  the  maximum  fuel  efficiency  is  desired  the  variations  in  the  mix- 
ture must  be  very  slight  indeed.  Stoddard  is  authority  for  the  state- 
ment that  one  volume  of  gasoline  to  8,400  volumes  of  air  at  at- 
mospheric pressure,  is  a  good  mixture;  and  that  one  volume  of  gas- 
oline to  10,000  volumes  of  air  ceases  to  be  explosive.  If  less  than 
8,400  volumes  of  air  are  used  per  volume  of  gasoline,  some  of  the 
gasoline  will  emerge  unburned  at  the  exhaust.  Consequently,  it 
would  appear  that  the  mixture  even  under  ordinary  working  condi- 
tions must  vary  only  slightly  in  composition  in  order  to  obtain  satis- 
factory results.  The  quality  of  the  fuel  may  also  have  some  effect 
upon  the  character  of  the  mixture. 

Gasoline  as  it  appears  on  the  market  varies  somewhat  in  composi- 
tion. The  gasoline  sold  generally  at  the  present  time  will  show  a 
test  for  specific  gravity  of  from  sixty-eight  to  seventy  degrees  Baume, 
although  some  is  found  testing  even  lower  than  this.  The  boiling 


CARBURETORS.  7 1 

point  of  gasoline  is  also  a  variable  quantity,  ranging  from  one 
hundred  five  degrees  Fahrenheit  to  one  hundred  thirty-five  degrees. 
The  lighter  and  more  volatile  oils  show  a  higher  specific  gravity  and 
lower  boiling  point  To  illustrate  this  matter  of  the  gravity  test  I 
might  mention  the  fact  that  kerosene  tests  about  forty-eight  degrees, 
Baume,  while  the  gasoline  best  adapted  to  gas  machine  work  tests 
eighty-eight  degrees.  These  figures  represent  the  relative  weights 
of  a  unit  volume  of  the  liquid  in  comparison  with  pure  water,  all 
at  sixty  degrees  temperature. 

In  most,  if  not  all,  of  the  states  the  quality  of  both  the  gasoline 
and  kerosene  is  regulated  by  state  law  and  all  oils  offered  in  the  mar- 
ket are  inspected  by  the  state  oil  inspector  or  his  deputies.  The  high 
gravity  test  gasolines  are  more  volatile  than  the  low  test,  that  is, 
they  will  vaporize  more  readily  and  at  a  lower  temperature.  Con- 
sequently, for  a  high  speed  engine  like  an  automobile  engine  the 
high  test  oils  give  somewhat  better  results.  They  are,  however,  ex- 
pensive, owing  to  the  fact  that  only  a  comparatively  small  quantity 
can  be  obtained  from  a  given  amount  of  crude  petroleum.  Pe- 
troleum is  a  very  complex  substance  chemically  consisting  of  a  large 
number  of  oils  of  different  densities.  These  are  separated  from  the 
crude  petroleum  by  the  process  of  distillation.  This  process  con- 
sists of  heating  the  crude  oil  to  a  certain  temperature  for  a  given 
length  of  time  until  all  that  will  be  vaporized  at  that  temperature  has 
been  driven  off.  The  resulting  vapors  are  condensed  in  suitable  con- 
densors,  purified,  and  placed  on  the  market  as  gasoline,  naphtha, 
kerosene,  lubricating  oils,  etc.  After  each  group  or  class  of  oils 
has  been  separated,  the  temperature  is  raised  and  the  next  class  is 
vaporized.  Each  one  of  these  classes  is  also  a  complex  structure 
since  the  range  of  temperature  used  in  the  separation  of  each  class 
causes  several  oils  of  different  densities  to  be  vaporized.  This  be- 
comes evident  at  once  to  any  one  who  has  had  much  experience  in 
running  gasoline  engines.  Stale  gasoline  is  simply  gasoline  that  has 
lost  its  more  volatile  constituents  by  standing  for  a  long  time  ex- 
posed to  the  air.  It  resembles  kerosene  in  its  characteristics 
and  does  not  vaporize  and  carburete  readily  and  consequently 
it  is  difficult  to  get  an  engine  started  unless  new  gasoline  is  placed 
in  the  tank,  that  is,  if  the  engine  has  stood  idle  for  a  considerable 
period. 

The  vaporizing  of  gasoline,  kerosene  or  alcohol  is  accomplished 
with  heat,  just  as  steam  is  formed  in  the  boiling  of  water.  Since 
the  boiling  point  of  the  three  first  named  liquids  is  much  lower  than 
that  of  water,  they,  of  course,  do  not  require  as  much  heat  as  an 


72  GASOLOGY. 

equal  quantity  of  water.  Nevertheless,  a  considerable  quantity  of 
heat  is  required  and  nearly  all  high  speed  engines  are  equipped  with 
carburetors  that  are  provided  with  an  auxiliary  air  intake  which 
draws  hot  air  from  around  the  cylinders  of  the  engine.  In  cold 
weather  this  is  essential  because  there  is  not  heat  enough  in  the 
air  to  vaporize  the  fuel. 

A  considerable  amount  of  trouble  is  often  experienced  in  cold 
weather  by  the  freezing  of  the  carburetor.  An  engine  will  run  for 
a  time  and  then  stop.  In  a  few  minutes  it  can  be  started  again  and 
will  run  for  a  considerable  time  before  the  carburetor  becomes  clog- 
ged with  ice  a  second  time.  The  freezing  of  the  carburetor  is  caused 
by  the  moisture  from  the  air  congealing  on  its  cold  surfaces.  Air 
always  contains  a  certain  amount  of  moisture  and  even  if  the  out- 
side air  is  nowhere  near  the  freezing  point,  freezing  of  the  car- 
buretor may  occur  with  a  high  speed  engine.  The  rapid  absorption 
of  heat  by  the  gasoline  vapor  on  its  way  through  the  carburetor 
may  lower  its  temperature  away  below  the  freezing  point.  We  have 
here,  on  a  small  scale,  the  same  principle  exemplified  as  in  the  am- 
monia refrigerating  machine.  In  this  the  liquid  ammonia  is  vap- 
orized with  the  rapid  absorption  of  heat  from  the  surrounding  sur- 
faces and  their  consequent  lowering  of  temperature. 

0 

LESSON  XXII. 

CARBURETORS. 

The  proper  mixing  of  the  fuel  takes  place  in  the  carburetor, 
This  is,  as  indicated  in  the  last  lesson,  a  rather  delicate 
process.  The  variation  in  the  quality  of  the  mixture  must  be 
very  slight  if  anything  like  good  results  are  to  be  obtained  in  the 
engine.  A  correct  proportion  of  air  and  gasoline  produces  a  gas 
whose  combustion  is  rapid ;  an  excess  of  air  makes  a  slow  burning 
mixture,  while  an  excess  of  gasoline  causes  not  only  slow  burning 
but  incomplete  burning  of  the  charge.  All  the  difficulties  of  back 
firing,  popping  in  the  muffler,  smoky  exhaust,  etc.,  are  mostly  due 
to  faulty  carburetion.  Back  firing  is  generally  caused  by  a  lean 
mixture,  which  is  so  slow  burning  that  it  is  not  completely  consumed 
at  the  end  of  the  power  stroke,  but  keeps  on  burning  in  the  com- 
pression space  until  the  inlet  valve  opens  on  the  suction  stroke. 
Then  the  flame  flashes  back  through  the  carburetor  and  causes  the 
phenomenon  known  as  back  firing.  This  may  become  exceedingly 
dangerous  if  there  is  a  leak  of  gasoline  around  the  tank  or  at  any 
of  the  points  in  the  gasoline  piping.  Many  automobiles  have  taken 
fire  and  not  a  few  have  been  completely  burned  through  just  this 


CARBURETORS. 


Cause.  A  slow  burning  charge,  due  to  an  over-rich  mixture,  some- 
times acts  in  a  similar  way,  but  it  always  causes  a  smoky  exhaust 
with  sooting  of  the  spark  plugs  and  the  inside  of  the  cylinder;  all 
of  which  causes  much  loss  of  time  and  annoyance  to  the  owner  of 
the  engine. 

If  the  same  kind  of  fuel  is  to  be  used  always  and  the  speed  of  the 
engine  can  be  kept  constant  it  is  not  difficult  to  construct  a  carbu- 
retor which  will  give  a  practically  constant  mixture,  or  at  least,  one 
whose  variations  are  si  slight1 
as  to  be  negligible;  but  when, 
engine  speed,  fuel,  temperature 
of  the  air,  and  everything  is 
variable,  it  makes  the  problem 
of  designing  a  carburetor  which 
will  successfully  meet  all  these 
conditions  exceedingly  difficult. 
There  are  some  very  good  car- 
buretors 011  the  market,  and 
some  that  give  excellent  results, 
but  there  is  still  much  to  be 
desired,  much  that  has  not  yet 
been  accomplished  -perhaps  is 
impossible  of  accomplishment — 
in  the  design  of  carburetors. 
Any  of  the  so-called  automatic 
carburetors  will  work  almost 
perfectly  for  any  given  speed 
when  adjusted  to  that  speed. 
They  will,  also,  on  account  of 
their  automatic  principle,  give 
fair  results  at  quite  widely 
varying  speeds,  but  there  is  no 

carburetor    made    that    will,    without    having    to    be    adjusted,    give 
equally  good  results  at  all  speeds. 

In  order  to  make  some  of  the  above  statements  clear  we  will  pro- 
ceed in  this  and  succeeding  lessons  to  describe  various  types  and 
styles  of  carburetors. 

One  of  the  simplest  carburetors  in  mechanical  construction  is 
the  spray  carburetor,  illustrated  in  Figs.  39  and  40.  It  consists 
of  a  conical  nozzle  A  whose  opening  may  be  regulated  by  the  needle 
valve  B.  The  level  of  gasoline  in  the  reservoir  C  is  maintained 
about  a  half  inch  below  the  level  of  the  needle  valve  by  means  of 
a  pump  which  pumps  the  gasoline  from  the  main  supply  tank. 


74 


GASOLOGY. 


The  gasoline  nozzle  projects  into  the  tipper  end  of  the  air  intake 
pipe  a  short  distance,  but  enough  so  that  all  the  air  passing  to  the 
cylinder  will  be  charged  with  the  vapor  of  gasoline. 

When  the  engine  piston  moves  outward  on  its  suction  stroke,  it 
causes  a  partial  vacuum  in  the  cylinder.  Atmospheric  pressure  causes 
air  to  rush  up  through  the  air  pipe  D  and  overcome  the  tension  of 

the  inlet  valve  spring  and  en- 
ter the  cylinder.  All  the  air 
which  enters  the  cylinder 
must  pass  through  the  pipe 
D  and  since  it  is  small  com- 
pared with  the  bore  of  the 
cylinder,  the  velocity  of  the 
air  must  be  quite  high.  In- 
deed, it  is  this  very  air  velo- 
city that  it  depended  upon 
to  lift  the  gasoline  from  res- 
ervoir C  to  the  nozzle  A, 
where  it  shoots  out  into  the 
moving  column  of  air  in  a 
fine  mist  or  spray.  The  higher 
the  velocity  of  the  current  of 
air  past  the  nozzle  the  greater 
will  be  the  pumping  effect 
and  the  larger  will  be  the 
amount  of  gasoline  pumped. 
This,  then,  is  the  reason  why, 
with  a  carburetor  of  this  kind, 
a  damper,  or  air  throttle,  is 
placed  in  the  air .  pipe  D. 
This  damper  must  always  be  closed  when  the  engine  is  started  by 
hand  in  order  to  reduce  the  size  of  the  air  pipe  enough  to  make 
the  velocity  of  the  air  sufficient  to  pump  gasoline  through  the  supply 
nozzle.  The  reason  for  this  increase  in  velocity,  due  to  throttling, 
will  become  at  once  apparent  when  one  considers  that  the  cylinder 
must  be  completely  filled  with  air  at  practically  atmospheric  pressure 
on  each  suction  stroke.  If  the  piston  moves  slowly  and  the  air  pipe 
is  large  the  air  will  move  slowly  through  the  pipe,  but  if,  on  the 
contrary,  the  size  of  the  air  pipe  is  greatly  reduced  by  an  air  throttle 
or  damper,  the  velocity  of  air  must  be  greatly  increased  in  order  to 
fill  the  cylinder.  If  the  air  throttle  were  left  closed  after  the  engine 
came  up  to  speed,  the  increased  pumping  effect  would  be  so  great 


FIG.  40. 


CARBURETORS.  75 

that  the  charge  would  be  too  rich,  even  though  the  cylinder  were  filled 
at  practically  atmospheric  pressure. 

Again,  let  us  suppose  that  the  needle  valve  of  a  carburetor  similar 
to  the  one  illustrated  were  adjusted  for  a  speed  of  say  400  revolu- 
tions per  minute  and  the  engine  was  running  satisfactorily  at  that 
speed.  If  we  should  increase  the  speed  of  the  engine  to  800  or  900 
revolutions  we  would  find  the  mixture  too  rich  because  of  the 
greater  pumping  effect  and  it  would  be  necessary  to  partly  close  the 
fuel  valve  in  order  to  get  the  same  mixture  as  before. 

In  stationary  engine  practice  there  is  little  or  no  trouble  with  the 
carburetor  on  account  of  variations  in  engine  speed  because  the  gov- 
ernor may  be  depended  upon  to  keep  the  speed  of  the  engine  constant, 
but  in  the  case  of  automobiles,  motor  boat  engines,  and  engines  of 
a  similar  class,  it  is  necessary  to  fit  them  with  a  carburetor  which 
will  automatically  take  care  of  the  variations  in  speed. 

LESSON  XXIII. 

In  the  last  lesson  attention  was  called  to  the  pumping 
effect  at  the  nozzle  of  the  carburetor,  caused  by  the  high  velocity 
of  the  air  rushing  into  the  cylinder.  This,  however,  is  only  one  of 
the  forces  impelling  the  gasoline.  The  other  is  atmospheric  pres- 
sure. When  the  piston  moves  outward  on  its  suction  stroke  a  partial 
vacuum  is  created  behind  the  piston,  the  admission  valve  opens 
under  the  influence  of  the  weight  of  the  atmosphere,  and  air  rushes 
into  the  cylinder.  The  pressure  in  the  cylinder  during  the  charg- 
ing stroke  is  at  all  times  less  than  that  of  the  atmosphere  and  con- 
sequently there  is  some  rarification,  or  reduction  in  pressure  of 
the  air  below  that  of  the  atmosphere,  around  the  end  of  the  gaso- 
line nozzle,  while  full  atmospheric  pressure  exists  on  the  top  of 
the  fuel  in  the  reservoir.  This  difference  in  the  pressure  head,  due 
to  the  rarification  or  reduction  of  pressure  in  the  cylinder,  plus  the 
velocity  head,  or  the  reduction  of  pressure  at  the  nozzle,  caused  by 
the  velocity  of  the  air,  are  the  two  forces  which  serve  to  project  the 
fuel  out  of  the  nozzle.  The  intensity  of  these  two  forces  depends 
upon  a  number  of  conditions,  as  will  presently  be  shown. 

These  forces  at  best  are. small  and  a  very  slight  change  in  condi- 
tions is  apt  to  affect  the  results  materially.  For  example,  a  slight 
change  in  the  height  of  the  fuel  in  the  reservoir  will  reduce  the 
pressure  head,  while  any  change  in  the  velocity  of  the  air  current 
passing  through  the  carburetor,  due  to  change  in  the  piston  speed, 
will  affect  the  velocity  head  and  consequently  the  amount  of  fuel 
used.  These  are  perhaps  the  two  principal  factors  governing  the 


76 


GASOLOGY. 


operation  of  spray  carburetors  of  whatever  class.  Other  factors, 
such  as  the  density  of  air,  the  amount  of  moisture  it  contains  and  its 
temperature,  all 
have  an  influence 
on  carburetor  per- 
formance and  serve 
as  evidence  of  the 
truth  of  the  state- 
ment in  the  last  les- 
son, that  it  is  very 
difficult,  if  not  im- 
possible, to  make  a 
carburetor  self  ad- 
justing to  all  con- 
ditions of  load,  en- 1 
gine  speed  and' 
weather. 

In  the  carburetor 
shown  in  the  last 
lesson  the  height  of 
fuel  is  kept  practic- 
ally constant  by  be- 
ing pumped  into  a 
reservoir  which  is 
fitted  with  an  over- 
flow pipe  into  which 
it  discharges  on 
reaching  a  certain 
level.  This  matter 
of  a  uniform  level 
from  which  the  gas-  -pIQ  ^ 

oline    flows,    is,    as 

was  said  before,  very  important,  because  if  the  level  is  kept  constant 
the  pressure  head  will  be  constant. 

In  looking  into  the  history  of  carburetors  we  find  three  different 
types;  the  surface  carburetor,  bubbling  or  filtering  carburetor,  and 
the  spray  carburetor  or  vaporizer,  a  simple  form  of  which  we  have 
just  discussed.  The  surface  carburetor  was  arranged  so  that  the  air 
on  its  way  to  the  engine  passed  across  the  surface  of  the  fuel  and 
became  saturated  with  the  fuel  vapor.  The  objection  to  this  form 
of  carburetor  lay  in  the  fact  that  only  the  lighter  portions  of  the 
fuel  became  volatilized,  the  heavier  portion  never  being  used  at  all. 


CARBURETORS. 


77 


In  the  bubbling  type,  the  air  was  caused  to  bubble  up  through  the 
fuel.  Here  the  same  objection  was  encountered  as  in  the  surface 
carburetor;  the  Volatile  portion  only  of  the  fuel  was  used,  while 
the  heavier  portion  remained  behind.  The  spray  carburetor  or  atom- 
izer has  the  advantage  of  utilizing  all  of  the  fuel  by  projecting  the 
whole  mass  into  the  air  where  it  is  either  entirely  vaporized  or 
broken  up  into  a 
fine  mist  and  car- 
ried directly  to  the 
cylinder.  Practically 
all  gasoJine  carbu- 
retors at  the  present 
time  belong  to  the 
last  named  class. 
There  are,  however, 
many  modifications 
in  design  with  a 
view  of  adapting 
them  to  different 
conditions  or  to 
making  them  auto- 
matic, which  we  will 
proceed  to  discuss 
in  this  and  subse- 
quent lessons. 

Figure  41  is  an 
example  of  a  very 
simple  form  of  mix- 
ing valve  or  carbu- 
retor. It  consists  of 
a  straight  brass  cast- 
ing provided  with  a 
valve  which  is  held  -pio  42 

in     position     by     a 

light  helical  spring  whose  tension  is  such  that  it  readily  opens  by 
suction  when  the  piston  starts  on  its  charging  stroke.  Gasoline  is 
fed  in  through  the  needle  valve,  either  under  pressure  or  by  gravity. 
The  amount  delivered  to  the  engine  is  regulated  in  the  usual  way 
with  the  milled  head  needle  valve.  If  this  is  opened  a  certain 
amount,  gasoline  will  flow  in  as  far  as  the  valve  seat,  where  it  is 
stopped  by  the  main  valve.  Then,  when  air  rushes  through  the 
carburetor  on  its  way  to  the  engine,  it  opens  the  main  valve  and 
picks  up  a  certain  amount  of  gasoline.  This  carburetor  valve  is 
particularly  well  adapted  to  a  gravity  feed, 


IV\A  I  N    AIR 
PORTS 


78  GASOLOGY. 

Another  style  of  mixing  valve  of  somewhat  similar  nature  is  shown 
in  Fig.  42  in  which  a  ball  valve  is  used  instead  of  a  cone  seated 
valve.'  Gasoline  is  fed  in  below  the  ball.  When  air  passes  up 
through  the  main  air  ports  the  ball  revolves,  and  a  fine  spray  of 
gasoline  comes  up  around  it.  The  lift  of  the  ball  can  be  regulated 
by  means  of  a  cam  attached  to  the  cross  shaft  just  above  it.  A  milled 
head  thumb  nut,  shown  on  the  left,  makes  the  proper  adjustment. 
Auxiliary  air  ports  are  provided  above  the  ball  valve  to  obtain  the 
proper  explosive  mixture  by  admitting  an  additional  amount  of  air 
into  the  charge,  while  a  throttle  valve  is  provided  to  control  the 
quantity. 

LESSON  XXIV. 

FLOAT    FEED    CARBURETORS. 

All  of  the  carburetors  used  on  automobiles,  most  of  those 
used  on  marine  engines,  and  many  that  are  used  on  station- 
ary engines  are  of  the  float  feed  automatic  type.  They  are 
spray  carburetors  or  vaporizers,  in  so  far  as  projecting  the  mass  of 
gasoline  directly  into  the  ingoing  current  of  air  is  concerned,  and 
they  obey  all  the  laws  for  carburetors  of  this  class  laid  down  in  the 
preceding  lessons,  but  they  differ  from  the  simple  carburetors  which 
were  described,  in  these  particulars.  They  maintain  a  fairly  uniform 
pressure  head  of  gasoline  by  not  permitting  it  to  rise  above  a  certain 
height  in  the  reservoir,  and  they  undertake  to  regulate  the  quality 
of  the  mixture  at  all  speeds  of  the  engine  and  under  a  wide  range 
of  varying  conditions  by  maintaining  the  same,  or  practically  the 
same  degree  of  vacuum  around  the  point  of  the  spray  nozzle.  The 
means  by  which  these  two  things  are  accomplished  can  best  be  ex- 
plained in  connection  with  Fig.  43,  which  represents  the  main 
essentials  of  a  float  feed  carburetor. 

Gasoline  is  delivered  to  the  float  chamber  by  gravity  from  a  tank 
placed  a  little  above  the  cylinder  of  the  engine.  The  float  consists 
of  a  thin  copper  vessel  closed  on  all  sides  with  all  joints  carefully 
soldered  to  prevent  any  liquid  from  reaching  its  interior. 

Sometimes  instead  of  using  a  metal  float,  a  cork  float  is  used.  If 
cork  is  used  it  must  be  well  shellaced  to  prevent  it  from  becoming 
saturated  with  gasoline  and  losing  its  buoyancy.  When  so  treated, 
however,  it  is  very  serviceable  and  will  remain  in  good  condition 
a  long  time.  The  metal  float  is  a  very  good  float  as  long  as  it  re- 
mains tight.  It  may  be  good  for  years  and  it  may  develop  a  leak 
in  a  few  weeks.  A  very  small  leak  is  much  more  troublesome,  being 


CARBURETORS. 


79 


harder  to  find  than  a  large  one.  In  every  case  the  function  of  the 
float  is  to  operate  a  valve  which  admits  gasoline  into  the  float  cham- 
ber. This  may  be  accomplished  in  one  of  several  ways.  In  Fig.  43, 
the  valve  stem  passes  easily  through  the  float.  A  grooved  collar  is 
secured  near  its  upper  end  which  affords  a  means  of  connection  for  a 
couple  of  weighted  levers  pivoted  at  P.  When  the  gasoline  falls  in 


GASOLINE, 


FIG.  43.     Elements  of  a  Float  Feed  Carburetor. 

the  float  chamber  the  float  also  falls,  allowing  the  weights  on  the  ends 
of  the  levers  to  drop  and  lift  the  valve  V,  thus  admitting  more  gaso- 
line. When  the  float  rises  it  pushes  up  on  the  weights  and  forces 
the  valve  to  its  seat. 

Two  other  methods  of  arranging  the  float  and  valve  appear  in  Figs. 
44  and  45.  The  arrangement  of  the  float  and  its  valve  is  so  obvious 
in  Fig.  44  that  no  detailed  explanation  seems  necessary. 

In  the  case  of  Fig.  45,  we  have  a  cork  float  arranged  in  the  form 
of  a  horse  shoe,  surrounding  the  central  air  tube  or  mixing  chamber. 

In  many  carburetors  there  is  some  device  to  provide  for  raising 
or  lowering  the  level  of  the  liquid  in  the  float  chamber  by  raising  or 
lowering  the  float. 


80 


GASOLOGY. 


In  Fig.  43  the  grooved  collar  may  be  shifted,  in  Fig.  44  the  float 
itself  can  be  set  at  the  required  height  by  shifting  the  nuts  on  the 
threaded  valve  stem,  but  in  Fig.  45  there  is  no  way  provided  to 
change  the  position  of  the  float. 

When  the  piston  moves  from  the  head  end  of  the  cylinder,  the 
pressure  of  the  gas  behind  it  drops  somewhat  below  atmospheric  pres- 
sure. When  it  moves  far  enough  so  that  the  difference  in  pressure 

between  the  atmosphere  and  the 
gas  inside  of  the  cylinder  is  great- 
er than  the  tension  of  the  inlet 
valve  spring,  then  the  latter  will 
open  and  the  charge  will  begin  to 
enter  the  cylinder.  The  pressure 
in  the  inlet  pipe,  right  close  to 
the  cylinder,  is  practically  the 
same  as  in  the  cylinder  and  gradu- 
ally increases  to  practically  atmos- 
pheric pressure  at  the  entrance. 

If  the  piston  could  be  made  to 
move  to  the  crank  end  of  the  cyl- 
inder instantly,  the  reduction  in 
gas  pressure  would  occur  instantly, 
and  the  amount  of  reduction  in 
the  inlet  pipe  or  carburetor  would 
SLbe  much  greater  than  it  ever  is  in 
practice.  This  would  cause  a  very 

FIG.  44.    ValvIIttached  to  Float.   rapi?  ™sl '  °f air  P."?*  *e  g,as.olin« 

nozzle   and   this  with   the   help   ot 

atmospheric  pressure  on  top  of  the  gasoline  in  the  reservoir  would 
cause  a  more  than  usual  flow  of  gasoline  for  the  given  quantity  of 
air.  In  other  words  the  mixture  would  be  very  rich.  This,  of  course, 
is  the  limiting  condition  in  that  direction,  but,  it  is  easy  to  see  that 
as  we  approach  this  condition  in  actual  practice,  by  means  of  high 
speed  we  must  find  some  way  to  bring  the  mixture  back  to  its  proper 
working  composition.  This  is  accomplished  by  means  of  what  is 
called  an  automatic  air  valve  as  shown  in  Fig.  43,  which  is  held  to 
its  seat  by  means  of  a  light  spring.  This  spring  is  given  a  certain 
amount  of  tension  and  holds  the  valve  shut  until  the  pressure 
above  the  spray  nozzle  falls  to  a  point  where  the  tension  of  the 
spring  is  not  sufficient  to  hold  the  valve  shut.  When  this  point 
is  reached,  air  rushes  through  the  auxiliary  air  port  and  to  a  certain 
extent  at  least  corrects  the  quality  of  the  mixture,  first  by  dilut- 
ing it  with  fresh  air,  and  second  by  preventing  too  great  a  reduc- 
tion of  pressure  in  the  mixing  chamber. 


CARBURETORS. 


81 


That  certain  defects  exist  in  this  method  of  controlling  the  quality, 
is  freely  admitted  by  every  one  who  is  at  all  acquainted  with  the 
working  of  carburetors.  There  is  no  exactitude  in  the  process  of 
mixing  the  air  and 
the  gasoline.  The 
mixture  is  first 
made  over-rich  and 
then  it  is  diluted  a 
certain  amount.  At 
slow  speeds  the  aux- 
iliary valve  does  not 
open,  consequently, 
from  that  point  up 
to  the  point  where 
it  does  work,  the 
mixture  is  incorrect 
—  not  very  much 
wrong,  of  course — 
but  yet  not  quite 
right.  Then  at  still 
higher  speeds  the 
mixture  is  made  so 
very  rich  that 
enough  air  can  not 
pass  through  the 
auxiliary  air  'port. 
To  be  sure,  the  , 
carburetor  can  be  FlG'  45'  One  style  °f  Automatlc  Carburetor, 
adjusted  for  this  higher  speed  all  right  enough,  but  the  point  I 
.wish  to  make  is  that  it  is  only  automatic  within  a  certain  range, 
and  through  only  a  small  portion  of  that  is  it  able  to  qualify  with 
any  great  degree  of  exactness. 

The  density  of  the  air,  its  humidity  and  its  temperature,  all  of 
these  things  have  an  important  bearing  on  the  operation  of  the  car- 
buretor and  all  taken  together,  make  it  difficult  to  construct  one 
that  is  able  to  adjust  itself  to  all  conditions,  automatically,  and  pro- 
duce a  uniform  mixture. 

LESSON  XXV. 

If  you  will  refer  to  lesson  XXIII,  you  will  find  in  Fig.  43  that  the 
gasoline  reservoir  is  placed  at  one  side  of  the  spray  chamber,  while  in 
Fig.  44  surrounds  that  chamber. 


82 


GASOLOGY. 


In  some  of  the  preceding  lessons  it  was  pointed  out  that  it  was 
very  essential  to  maintain  a  constant  level  of  gasoline  in  the  float 
chamber,  and  especially  that  this  level  should  remain  constant  with 
reference  to  the  spray  nozzle.  In  carburetors  of  the  type  shown  in 
Fig.  43,  difficulty  is  experienced  in  this  respect  whenever  one  wheel 
of  the  car  runs  in  the  ditch  along  the  side  of  the  road,  or  when  the 
car  moves  along  the  side  of  a  hill,  because  there  is  a  distance  of  two 

inches  or  more  between  the  float 
chamber  and  the  spray  nozzle. 
The  carburetor  shown  in  Fig. 
45  is  the  result  of  an  effort  to 
overcome  this  difficulty  by  mak- 
ing the  float  surround  the  spray 
nozzle.  In  this  construction  the 
latter  occupies  the  center  of 
the  reservoir,  a  position  where 
the  level  of  the  liquid  remains 
most  nearly  constant,  and  where 
the  rocking  of  a  boat  or  the  tilt- 
ing of  an  automobile  will  affect 
the  level  of  gasoline  at  the 
nozzle  very  little. 

The  automatic  principle  men- 
tioned in  the  last  lesson  is  car- 
ried out  in  a  different  manner 
FIG.  46.  in     different     carburetors;     for 

example,  in  Fig.  45,  the  air  at 

slow  engine  speed  has  low  velocity  and  cannot  overcome  the  tension 
of  the  spring  holding  the  auxiliary  valve  to  its  seat. 

Under  these  conditions  enough  air  can  enter  through  the  open 
space  below  the  auxiliary  valve.  When  the  speed  of  the  engine  in- 
creases and  the  vacuum  in  the  spray  chamber  becomes  greater,  the 
rush  of  air  through  the  air  intake  opens  the  auxiliary  valve  and  al- 
lows the  entrance  of  a  larger  volume  of  air.  The  effect  of  the  high 
vacuum  in  the  spray  chamber,  together  with  the  rapid  inrush  of  air 
is  sufficient  to  produce  a  mixture  that  would  be  too  rich  to  be  ex- 
plosive, hence  the  necessity  of  reducing  the  richness  by  the  admixture 
of  fresh  air,  either  in  the  manner  above  specified  or  in  some  other 
manner. 

There  has  been  placed  on  the  market  quite  recently,  a  carburetor  in 
which  the  air  passes  through  different  sized  openings  normally  closed 
by  ball  valves.  The  larger  balls,  exposing  the  greater  area  in  propor- 


CARBURETORS. 


83 


air  valve 


tion  to  their  mass,  will  lift  first,  and,  as  the  speed  of  the  engine  in- 
creases, thus  causing  a  higher  vacuum,  the  other  smaller  balls  open 
and  more  air  is  admitted.  Here,  as  in  Eig.  45,  the  air  all  passes 
through  the  spray  chamber.  A  sectional  view,  showing  principles  of 
the  above  described  carburetor,  appears  in  Fig.  46. 

Fig.  47  represents  another  style  of  automatic  carburetor,  in  which 
the  auxiliary  air  supply  is  admitted  at  some  distance  beyond  the 
spray  nozzle.  In  order  to  facilitate  and  insure  proper  mixing,  the 
auxiliary  air  is  admitted  at  right  angles  to  the  main  current.  This 
sets  up  eddy  currents,  and  the  whole  mass  is  supposed  to  become 
thoroughly  mixed. 

There  are  two  other 
features  in  this  car- 
buretor that  deserve 
more    than    passing 
notice.     The  first  is 
the     shape     of    the 
chamber  around  the 
spray    nozzle.      The 
air      which      enters 
around  the  cup  be-  ^ 
low   passes   through  ^ 
a     chamber    shaped  § 
in  such  a  way  that  & 
the  greatest  velocity  ' 
of   the    air    will   be 
just  beyond  the  end 
of  the  gasoline  noz- 
zle.    This  construc- 
tion   tends    also    to 
cause  all  of  the  air 

to  be  saturated  with  the  spray  of  gasoline,  which  spreads  out  in  can- 
opy form  from  the  top  of  the  nozzle. 

The  other  feature  to  which  we  referred  is  the  annular  hot  water 
chamber  surrounding  the  spray  chamber.  This  is  arranged  to  be 
connected  to  the  cylinder  jacket  and  keeps  the  carburetor  hot  in 
cold  weather.  This  aids  in  vaporizing  the  fuel  and  makes  the  use 
of  the  ordinary  sixty-eight  degrees  gasoline  effective  on  high  speed 
cars  in  moderately  cold  weather.  As  stated  in  a  previous  lesson,  the 
vaporization  of  any  liquid  necessitates  using  a  considerable  quantity 
of  heat  which  must  be  abstracted  either  from  the  incoming  air  or 
else  from  some  other  source.  When  the  out-of-doors  temperature  is 


Air  intake. 


FIG.  47. 


84 


GASOLOGY. 


well  below  freezing  there  is  very  little  heat  in  the  air  with  which 
to  effect  vaporization,  and  some  other  source  is  imperative,  especially 
for  high  speed  engines. 

In  the  case  of  most  carburetors  the  piping  is  so  arranged  that  the 
air  can  be  taken  from  around  the  hot  cylinders  in  cold  weather,  or  by 
means  of  a  by-pass  valve  the  hot  air  supply  can  be  cut  off  and  cold  air 
substituted,  thus  making  the  carburetor  suitable  for  either  summer 
or  winter  use. 


FIG.  48. 

It  is  true  that  a  large  weight  of  mixture  will  be  taken  into  the 
cylinder  when  the  air  is  quite  cool,  but  even  with  air  that  is  heated 
to  above  one  hundred  degrees,  there  is  no  question  but  that  the  vapor- 
ization of  the  gasoline  cools  it  down  close  to  the  freezing  point. 

When  such  low  temperatures  are  encountered,  there  doubtless  is 
considerable  gasoline  taken  into  the  cylinder  in  the  shape  of  minute 
globules.  These  must  be  vaporized  inside  of  the  cylinder  and  there  is 
no  certainty  that  there  is  sufficient  air  to  effect  their  complete  com- 
bustion. It  is  much  better,  therefore,  where  a  carburetor  is  used  at 
all,  to  have  the  vaporization  completed  therein  and  to  supply  the 


CARBURETORS.  85 

engine  cylinder  with  a  dry  gas.  A  carburetor  meeting  these  speci- 
fications will  prove  most  economical  in  the  use  of  gasoline. 

In  one  of  the  earlier  lessons  of  these  series  we  pointed  out  that 
practically  all  of  the  carburetors  in  use  at  the  present  time  are 
spray  carburetors,  and  that  the  earlier  forms  of  surface  and  bubbling 
carburetors  had  been  displaced  and  the  reason  therefor  pointed  out. 
There  are,  however,  a  few  carburetors  now  on  the  market,  which  have 
come  into  some  prominence  quite  recently,  in  which  advantage  is 
taken  of  the  principles  of  the  surface  carburetor.  While  these  prin- 
ciples are  made  use  of,  they  are  modified  in  such  a  way  as  to  obviate 
the  inherent  difficulties  of  the  older  type  of  machine. 

The  carburetor  illustrated  in  Fig.  48  is  an  example  of  one  of  these 
carburetors.  At  slow  engine  speeds  it  is  a  surface  carburetor.  Air 
enters  through  the  primary  air  ports  at  A  in  the  right  hand  figure, 
and  becomes  enriched  by  passing  over  the  puddle  of  gasoline  at  B. 
When  the  throttle  is  opened  and  the  engine  comes  up  to  speed,  the 
auxiliary  air  valve  0  is  opened,  air  rushes  through  the  auxiliary  air 
intake  and  causes  a  pumping  effect  at  the  nozzle  which  lifts  the  level 
of  gasoline  in  the  spray  nozzle,  causing  numerous  fine  jets  of  the 
liquid  to  be  projected  into  the  rapidly  moving  column  of  air. 
The  higher  the  engine  speed,  the  higher  the  gasoline  rises.  This 
puts  more  jets  in  operation,  with  the  result  that  a  larger  quantity  of 
gasoline  is  used,  but  the  proportion  is  supposed  to  be  adjusted  cor- 
rectly to  the  quantity  'of  air  flowing  through  the  intake  pipe.  A 
float  maintains  the  gasoline  at  any  desired  level,  while  a  milled  head 
screw  in  the  center  adjusts  the  gasoline  for  high  engine  speeds, 
while  the  automatic  air  valve  takes  care  of  slower  speeds. 

There  is  another  carburetor  on  the  market  in  which  the  same  prin- 
ciple is  applied  in  another  way.  This  is  a  carburetor  used  quite  ex- 
tensively for  marine  engines  where  it  is  said  to  give  good  service.  A 
float  valve  maintains  a  constant  level  of  gasoline,  but  instead  of  using 
a  nozzle  to  supply  gasoline  to  the  air,  a  very  narrow  annular  opening 
in  the  bottom  of  the  hole,  said  to  be  only  one  five  thousandths  of  an 
inch  wide,  is  made  use  of.  When  the  engine  is  standing  idle,  gasoline 
accumulates  in  a  puddle  in  the  bottom  of  the  bowl.  When  the  engine 
starts,  the  air  passing  through  the  intake  pipe  with  considerable  ve- 
locity impinges  upon  the  gasoline  with  considerable  force,  as  it  must 
do  in  order  to  change  its  direction  completely  and  pass  through  the 
supply  pipe  to  the  engine. 

This  operation  produces  a  rich  mixture  which  is  necessary  for 
starting  or  running  at  slow  speeds.  When  the  engine  comes  up  to 


86  GASOLOGY. 

speed,  the  puddle  is  all  evaporated  and  a  fine  jet  or  curtain  of  gaso- 
line is  projected  into  the  air. 

Economizers. — In  connection  with  any  discussion  of  carburetors 
the  story  is  not  all  told  until  economizers  are  considered.  These  are 
devices  whose  office  it  is  to  prevent  excessive  fluctuations  in  the 
pumping  effect  at  the  spray  nozzle  under  wide  variations  of  speed. 
This  is  accomplished  by  partially  equalizing  the  pressures  at  the 
three  points;  just  above  the  spray  nozzle,  between  the  throttle  and 
the  engine,  and  the  space  above  the  fuel  in  the  gasoline  reservoir. 
The  economizer  is  screwed  into  the  cap  of  the  gasoline  reservoir  and 
two  pipes  are  led  out,  one  to  a  point  below  the  throttle  and  the 
other  to  a  point  above.  Any  sudden  movement  of  the  throttle,  there- 
fore, will  not  affect  to  any  great  extent  the  quantity  of  gasoline  de- 
livered at  the  spray  nozzle,  because  a  partial  vacuum  exists  above 
the  gasoline,' which  prevents  a  flood  of  gasoline  being  delivered. 


CHAPTER  IX 
HORSE  POWER  FORMULAS 

LESSON  XXVI. 

Horse  power  and  work  and  what  an  engine  can  pull  are  three  things 
that  are  hard  to  explain  in  simple  language  which  non-technical  peo- 
ple can  understand,  but  we  are  going  to  try  it.  Every  mail  brings 
us  requests  for  information  about  how  to  estimate  the  horse  power  of 
an  engine,  and  in  every  case  all  we  can  do  is  to  make  the  estimate 
without  going  into  explanations.  That  is  why  we  are  taking  this 
opportunity  to  present  a  lesson  on  the  subject.  We  can  go  into  the 
subject  much  more  fully  and  show  some  of  the  reasons  why  we  make 
certain  computations. 

Almost  everyone  knows  that  a  horse  power  is  equivalent  to  doing 
thirty-three  thousand  foot  pounds  of  work  in  one  minute,  but  there 
are  many  people  who  apparently  fail  to  take  account  of  the  factor 
time.  Furthermore,  everyone  may  not  know  the  meaning  of  the 
term  foot  pounds.  Consequently,  we  will  start  our  discussion  with 
the  statement  that  a  foot  pound  is  equal  to  overcoming  a  resistance 
of  one  pound  through  a  distance  of  one  foot.  Work  is  merely  the 
overcoming  of  resistance  through  distance,  therefore  the  foot  pound 
is  the  measure  of  the  amount  of  work  done,  since  it  takes  into  ac- 
count the  amount  of  resistance  as  well  as  the  distance.  A  horse 
power  not  only  takes  into  account  the  work  done  in  foot  pounds,  but 
the  time  it  takes  in  which  to  accomplish  the  work.  A  horse  power, 
therefore,  is  a  measure  of  the  rate  at  which  work  is  done.  In  fact, 
whenever  we  talk  about  power  in  any  form,  we  are  taking  into  ac- 
count the  factor  time  or  the  rate  at  which  work  can  be  done.  That, 
then,  is  the  significance  of  the  term  horse  power,  a  measure  of  the 
rate  of  doing  work.  The  man  or  the  machine  that  can  do  work 
the  fastest  has  the  most  power.  The  amount  of  work  ultimately  ac- 
complished is  no  measure  of  the  power  applied  unless  the  factor 
time  is  taken  into  account.  A  machine  that  can  do  twice  as  much 
work  in  the  same  time  must  have  twice  as  much  power. 

Let  us  now  consider  more  in  detail  the  meaning  of  the  term  work. 
According  to  the  definition  just  given,  it  consists  of  two  factors, 
force  and  distance.  Force  is  expressed  in  pounds,  distance  in  feet, 
and  work  in  foot  pounds.  We  could,  if  we  wanted,  express  force  in 


88  GASOLOGY. 

tons  and  distance  in  miles  and  the  work  would  be  expressed  in  ton 
miles,  but  for  our  purpose  in  the  discussion  of  horse  power  we  will 
confine  ourselves  to  pounds  and  feet.  In  order  to  find  out  how  much 
work  is  accomplished  in  any  given  operation  all  that  is  necessary  to 
do  is  to  multiply  force  by  the  distance  through  which  this  force 
is  exerted;  for  example,  suppose  it  takes  a  force  of  two  hundred 
pounds  to  move  a  wagon  on  a  level  road,  and  that  the  distance  moved 
is  twenty-four  feet;  how  much  work  will  be  done?  The  result  is 
obtained  by  multiplying  the  two  factors  together;  thus:  200x24= 
4,800  foot  pounds  of  work.  ,  Again,  suppose  a  man  weighing  one 
hundred  and  sixty  pounds  climbs  a  ladder  twelve  feet  high;  how 
much  work  does  he  do?  Here  again  we  multiply  the  force  by  the 
distance  through  which  it  acts  and  find  that  the  man  accomplishes 
1,920  foot  pounds  of  work.  These  examples  should  suffice  to  explain 
the  meaning  of  the  term  work. 

Now,  let  us  turn  our  attention  to  power  for  a  moment  and  try  to 
obtain  a  clear  conception  of  what  it  signifies  by  taking  some  con- 
crete examples.  Take  for  example  the  case  of  the  man  going  up  the 
ladder.  If  he  went  up  in  one  minute  he  would,  as  before,  do  1,920 
foot  pounds  of  work,  no  more  and  no  less.  If  he  went  up  in  one-half 
minute  he  would  still  do  the  same  amount  of  work,  but  it  would 
require  twice  as  much  power  in  the  second  case  as  in  the  first  because 
the  time  is  only  half  as  much.  Power,  therefore,  depends  upon 
speed.  This  can  be  further  illustrated  in  this  way;  suppose  a  man 
has  a  ton  of  wheat  put  up  in  one  hundred  pound  sacks  which  he  must 
place  upon  a  table  three  feet  high.  The  amount  of  work  to  be  done 
is  six  thousand  foot  pounds.  If  he  lifts  all  of  them  up  in  one  min- 
ute, it  will  require  the  expenditure  of  a  certain  amount  of  power. 
If  he  lifts  them  all  up  in  one-half  minute  it  will  require  twice  as 
much  power,  but  no  more  work  is  done  in  one  case  than  in  the  other. 
It  will  require  a  stronger  man,  however,  to  do  the  work  more  rapidly, 
or,  even  if  a  weaker  man  can  accomplish  the  same  work  he  will  feel 
the  effects  of  the  strain  much  more. 

A  horse  power  has  already  been  defined  as  33,000  foot  pounds  of 
work  in  one  minute.  Any  engine  that  can  accomplish  this  amount 
of  work  in  one  minute  is  doing  one  horse  power  of  work.  If  the 
same  work  can  be  done  in  one-tenth  of  a  minute  it  will  require  a 
10-horse  power  engine  to  do  the  work.  Time,  then,  is  the  all  impor- 
tant consideration  in  all  matters  concerning  power. 

This  same  factor,  time,,  enters  into  all  considerations  of  the  trac- 
tive force  or  pulling  power  of  an  engine.  The  question  oftens  comes 
up :  How  much  will  an  engine  pull  on  the  road  ?  This  depends  upon 


HORSE  POWER — FORMULAS.  89 

a  number  of  variable  factors,  such  as  the  horse  power  of  the  engine, 
the  condition  of  the  road  bed,  the  power  lost  in  transmission,  the 
weight  of  the  machine,  the  grip  the  wheels  have  on  the  road,  and  the 
speed  of  the  engine.  This  latter  factor  is  the  one  that  proves  to  be 
a  stumbling  block  for  a  great  many  people.  Many  people  do  not 
realize  that  the  hauling  capacity  of  an  engine  decreases  in  exact 
proportion  to  its  speed.  That  is  why  in  going  up  a  steep  hill  it  is  nec- 
essary to  run  an  automobile  on  low  gear.  It  does  not  have  anymore 
power  when  so  run,  but  the  work  of  lifting  itself  up  the  hill  is  done 
in  a  longer  time,  and  consequently  less  power  is  required.  Likewise 
a  traction  engine  can  haul  a  larger  load  if  the  road  speed  is  slower. 
Other  things  being  equal,  an  engine  ought  to  be  able  to  pull  five 
times  as  much  at  one  mile  an  hour  as  it  can  at  five  miles  an  hour. 
In  either  case,  "the  same  number  of  foot  pounds  of  work  will  be  done, 
as  we  can  easily  prove.  Suppose  the  engine  is  capable  of  pulling 
one  ton  at  five  miles  an  hour;  the  work  done  is  five  ton  miles.  At 
one  mile  per  hour,  the  engine  should  be  able  to  haul  five  tons  and 
here  again  work  done  is  five  ton  miles  per  hour,  just  as  in  the  former 
case.  Slow  speeds  on  an  engine  enable  it  to  haul  a  heavier  load  and 
fast  speeds  a  lighter  load,  but  in  either  case  the  same  number  of  foot 
pounds  or  ton  miles  of  work  will  be  accomplished. 

Now  let  us  consider  some  of  the  formulas  for  horse  power.  The 
first  one  to  attract  our  attention  is  the  old  steam  engine  formula  for 
indicated  horse  power  with  which  every  one  is  familiar,  and  which 
reads  as  follows : 

1.    2XPXLXAXN 

=H.  P. 

33,000 

In  which  P  represents  the  average  force  acting  on  the  piston  in 
pounds;  L,  is  the  length  of  the  stroke  in  feet;  A,  is  the  area  of  the 
piston,  and  N  is  the  number  of  revolutions  of  the  engine  per  minute. 
The  factor  2  is  used  to  change  revolutions  into  strokes  when  a  double 
acting  engine  is  used.  If  the  engine  were  single  acting,  that  is,  had 
force  applied  only  on  one  side  of  the  piston,  this  factor  would  not 
enter.  In  this  formula  PxLxA  represents  the  work  done  in  foot 
pounds  during  one  stroke  of  the  piston.  This  multiplied  by  2xN 
gives  us  the  work  done  in  foot  pounds  in  one  minute.  If  this  product 
is  then  divided  by  33,000  we  will  evidently  obtain  the  number  of  horse 
power  the  engine  is  capable  of  developing.  This  is  a  strictly  mathe- 
matical unit,  and  is  invariable.  By  its  use  we  can  calculate  the 
power  of  any  reciprocating  engine,  whether  it  be  a  gas  engine  or  a 


90 

steam,  engine,  provided  we  can  find  the  value  of  the  factor  P.  This 
is  not  always  easy,  however.  We  can,  it  is  true,  use  an  indicator  and 
estimate  the  average  pressure  from  the  diagram  it  traces,  but  even 
this  is  not  always  reliable,  especially  in  the  case  of  a  gas  engine. 
When  the  power  is  obtained  in  this  way  we  have  a  measure  of  the 
power  developed  in  the  cylinder  of  the  engine,  but  not  the  power 
which  the  engine  will  develop  at  the  band  wheel.  That  will  always  be 
somewhat  less,  on  account  of  the  internal  friction  of  the  engine.  The 
only  way  to  obtain  the  power  the  engine  is  able  to  develop  to  do  ac- 
tual work  is  by  means  of  a  brake. 

Now  let  us  see  what  we  can  find  out  about  calculating  gas  engine 
horse  power.  The  formula  for  the  indicated  horse  power  of  a  gas 
engine  is 

PXLXAXE 

—  =H.  P. 


33,000 

The  formula  is  almost  the  same  as  for  the  steam  engine,  except  in- 
stead of  engine  strokes  we  use  E,  which  represents  explosions  in  the 
cylinder.  Just  as  in  steam  engine  practice,  the  value  of  P  must  be 
determined  by  the  use  of  an  indicator. 

After  you  have  taken  your  indicator  cards,  measured  them  and 
made  all  the  proper  allowances,  and  have  made  an  estimate  of  the 
mean  effective  pressure,  you  are  at  liberty  to  use  the  formula  and 
find  out  how  much  work  is  done  on  the  piston.  If  you  want  to  find 
out  how  much  work  the  engine  will  actually  do  at  the  fly  wheel,  you 
must  take  seventy-five  or  eighty  per  cent  of  the  above  result,  because 
anywhere  from  twenty  to  twenty-five  per  cent  of  the  work  done  on 
the  piston  is  required  to  overcome  the  friction  of  the  engine  itself, 
even  if  it  is  a  good  gas  engine  ;  and  if  it  isn't,  there  is  no  way  of  tell- 
ing except  after  you  have  found  the  indicated  power,  to  put  on  a 
brake  and  take  the  brake  horse  power.  The  difference  between  the 
brake  power  and  the  indicated  power  will  be  the  amount  of  work 
consumed  in  friction.  This  is  never  less  than  fifteen  per  cent  of 
the  total  power  developed  in  the  cylinder  and  often  as  high  as  thirty 
per  cent. 

There  is  another  way  of  getting  at  the  mean  effective  pressure 
by  the  use  of  what  is  known  as  Grover's  formula.  It  reads  thus  : 

2.    2C—  .01C2=M.  E.  P. 

In  this  formula  C  represents  the  compression  pressure  in  pounds 
above  the  atmosphere.  After  you  have  found  this  value  you  are  at 


HORSE  POWER  —  FORMULAS.  91 

liberty  to  use  it  in  formula  2  in  place  of  P.  After  you  have  done 
the  necessary  figuring,  you  are  in  a  position  to  make  a  fairly  close 
estimate  of  the  power  of  the  engine.  Of  course,  this  formula  is 
not  exact,  and  it  is  criticised  a  good  deal,  and  with  good  reason,  but 
it  has  some  merit  even  if  not  very  scientific. 

All  of  this  leads  up  to  another  class  of  formulas  known  as  em- 
pirical formulas,  that  is,  formulas  that  give  results  that  are  pretty 
close,  but  which  do  not  admit  of  any  scientific  explanation,  or  rather 
not  a  very  rigid  one  at  any  rate. 

These  formulas  are  divided  into  two  classes,  those  applicable  to 
four-cycle  engines  and  those  applicable  to  two-cycle.  We  will  con- 
sider the  four-cycle  formulas  first.  In  all  of  these  formulas  the 
symbols,  have  the  same  value  and  are  as  follows  : 

D  equals  the  diameter  of  the  cylinder  in  inches;  L,  the  stroke 
of  piston  in  inches;  E,  the  revolutions  of  the  crank  shaft  per  min- 
ute; N,  the  number  of  cylinders.  Using  these  symbols,  Roberts  offers 
the  following  formula  for  gasoline  engines: 


,3. 

—  H.  P. 

18,000 

The  Royal  Automobile  Club  uses  this  formula: 
4.     (D+L)2XN 


:H.      P. 


9.92 

The  American  Licensed  Automobile  Manufacturers  have  adopted 
a  slightly  different  formula,  which  reads  as  follows,  and  is  based  on 
a  piston  speed  of  1,000  feet  per  minute. 


5. 

—  =H.  P. 

2.5 

The  American  Power  Boat  Association  formula  for  motors  of  less 
than  six  inches  stroke  is  like  the  last  one  just  given  except  that  the 
length  of  stroke  is  taken  into  account. 


6. 

—  =H.  P. 

15.2 

The  last  two  formulas  are  for  motors  used  in  boats  rated  as  auto- 
mobile boats.     For  all  other  marine  motors  two-thirds  of  the  above 


92  GASOLOGY. 

results  are  to  be  taken.  Now  let  us  apply  these  formulas  to  an  engine 
with  a  four-inch  bore  and  five-inch  stroke,  running  at  1,200  revolu- 
tions per  minute. 

Applying  formula  3  we  have 

4X4X5X1200 

=5  1/3  H.  P. 

18,000 

By  formula  4  we  have  9X9 

=8.2 

9.92 

By  formula  5  we  have  4X4 

-=6.4 


2.5 
By  formula  6  we  have  4X5 


15.2 


=5.2 


An  inspection  of  the  above  results  does  not  show  very  close  agree- 
ment. As  a  matter  of  fact,  they  are  principally  valuable  in  determin- 
ing handicaps  in  a  race  and  for  purposes  of  comparison  rather  than 
to  give  results  that  have  a  definite  meaning. 

Two-cycle  formulas. 

7.  Roberts'.    D^X^X^XN 

— =H.  P. 
13,600 

8.  A.P.B.  A.     D2XN 

— =H.    P.    for   engine    having    six    inch 
2.1008 
stroke  or  greater. 

9.  A.P.B.A. 


12.987 

The  above  A.  P.  B.  A.  formulas  are  for  racing  boat  motors.  All 
other  marine  motors  use  the  same  formula  and  take  two-thirds  of  the 
results  above  obtained. 

Applying  these,  formulas  to  the  same  size  of  motor  as  in  the  four- 
cycle class,  we  obtain*  the  results  herewith  shown. 

By  formula  7,  7.11  H.  P.;  by  formula  9,  6.15.  These  two  formu- 
las do  not  appear  to  yield  much  closer  results  than  the  four-cycle 


HORSE  POWER — FORMULAS.  93 

formulas  just  discussed.  As  a  matter  of  fact,  Roberts'  two  formu- 
las are  probably  as  close  as  we  can  come  to  expressing  the  actual 
horse  power  of  a  gasoline  engine  by  means  of  a  formula.  They  do 
not  amount  to  much  more  than  a  fair  estimate  and  are  so  under- 
stood by  all  engineers  who  have  to  do  with  problems  of  this  kind. 

LESSON  XXVII. 

The  indicated  horse  power  of  an  internal  combustion  engine  is  a 
measure  of  the  actual  horse  power  developed  in  the  engine  cylinder. 
It  is,  in  other  words,  the  power  that  is  expended  upon  the  piston  and 
is  always  considerably  greater  than  what  can  be  obtained  from  the 
engine  in  useful  work  at  the  fly  wheel.  When  the  fuel  and  its  proper 
proportion  of  air  is  introduced  into  the  engine  cylinder  and  burned 
it  produces  a  very  high  temperature  of  the  gas  behind  the  piston. 
In  accordance,  therefore,  with  the  laws  of  heat  this  gas,  which  is  at 
the  given  instant  enclosed  in  a  small  space,  exerts  tremendous  pres- 
sure upon  the  walls  of  the  cylinder  and  upon  the  head  of  the  piston. 
In  the  case  of  ordinary  gasoline  engines  this  pressure,  at  the  moment 
the  piston  is  started  forward  on  its  power  stroke,  may  amount  to 
from  250  to  300  pounds  per  square  inch. 

The  exact  amount  of  the  initial  pressure  is  dependent  upon  a 
number  of  things,  among  which  may  be  mentioned  the  degree  of 
compression  of  the  charge,  the  temperature  of  the  gas  at  the  moment 
of  ignition,  the  degree  of  completeness  of  the  combustion  before 
the  piston  starts  forward  on  its  power  stroke,  and  the  quality  of  the 
mixture. 

If  the  gas  is  first  compressed  to  60  or  70  pounds  and  the  fuel  is 
capable  of  raising  the  pressure  200  pounds,  the  total  initial  pressure 
will  be  the  sum  of  the  two.  Consequently,  the  higher  the  compression 
pressure  with  any  given  fuel,  the  higher  will  be  the  initial  pressure; 
and,  within  certain  limits,  the  greater  the  power  of  the  engine.  It 
has  been  stated  in  nearly  every  book  treating  of  the  gas  engine  that 
its  efficiency  depends  very  largely  upon  the  degree  of  compression. 
It  can  be  proved  theoretically  that  the  higher  the  degree  of  compres- 
sion in  the  case  of  any  engine  working  on  the  Otto  cycle,  the  greater 
the  efficiency.  This  means  that  with  the  expenditure  of  a  given 
quantity  of  fuel  the  greatest  amount  of  work  can  be  obtained  when 
the  compression  is  carried  to  the  highest  point  possible.  This  is 
true,  regardless  of  the  kind  of  ;fuel  used.  Practically,  the  kind  of 
fuel  exerts  a  marked  influence  because  of  the  fact  that  compression 
cannot  be  carried  as  high  with  some  kinds  of  fuel  as  with  others. 
For  example,  gasoline  vapor  is  highly  inflammable  and  will  ignite 


94  GASOLOGY. 

at  lower  temperature  than  some  other  gas,  such  as  blast  furnace 
gas  or  producer  gas. 

In  ordinary  medium  speed  gasoline  engines  a  compression  pres- 
sure of  70  pounds  is  about  as  much  as  can  be  obtained  without  caus- 
ing pre-ignition.  If  the  engine  is  of  the  slow  speed  type,  compression 
pressures  as  high  as  80  or  85  pounds  are  often  carried  out  success- 
fully, while  with  the  high  speed  automobile  engines  a  compression 
of  60  pounds  is  customary.  It  requires,  therefore,  no  stretch  of  the 
imagination  to  realize  that  an  engine  suitable  for  one  kind  of  fuel 
may  not  be  suitable  for  another.  Furthermore,  an  engine  that  will 
produce  a  given  amount  of  power  with  one  kind  of  fuel  may  be  very 
inefficient  and  lack  a  great  deal  of  coming  up  to  its  power  specifica- 
tions when  another  kind  of  fuel  is  substituted.  This  can  be  explained 
easily  when  we  take  into  consideration  the  heat  values  of  some  of  the 
different  fuels. 

Gasoline  vapor  has  a  heat  value  of  about  650  heat  units  per 
cubic  foot;  producer  gas  from  90  to  125;  city  gas,  750  to  900;  and 
natural  gas  from  1,000  to  1,100.  An  engine,  therefore,  which  uses  a 
gas  of  high  heat  value,  such  as  natural  gas,  will  yield  considerably 
more  in  horse  power  than  the  same  engine  using  producer  gas,  for 
the  simple  reason  that  the  gas  containing  the  larger  number  of  heat 
units  contains  the  greater  amount  of  energy  which  may  be  set  free 
for  the  doing  of  useful  work. 

The  degree  of  completeness  of  combustion  before  the  piston  starts 
forward  on  its  power  stroke  has  much  to  do  with  the  initial  pres- 
sure. To  be  most  effective,  the  fuel  should  all  be  consumed  before 
the  piston  has  advanced  an  appreciable  amount  on  its  power  stroke. 
When  this  condition  obtains,  the  initial  pressure  will  be  the  maximum 
for  the  given  charge  of  fuel,  and  the  piston  will  be  driven  forward 
by  the  expansion  of  the  gas  solely  and  not  by  the  addition  of  more 
pressure  due  to  what  is  known  as  after-burning.  It  can  also  be  shown 
theoretically  and  it  has  been  proven  practically  that  the  best  results 
are  obtained  when  the  fuel  is  all  burnt  at  the  beginning  of  the  stroke 
and  the  expansion  is  adiabatic.  That  is,  when  no  heat  is  either  sup- 
plied or  taken  away  during  the  stroke.  It  naturally  follows  from  the 
construction  of  the  engine  and  its  method  of  operation  that  a  true 
adiabatic  expansion  cannot  be  obtained.  There  will  be  some  transfer 
of  heat  from  the  gas  to  the  cylinder  walls  at  the  beginning  of  the 
stroke  and  toward  the  end  of  the  stroke  there  may  be  a  flow  of  heat 
in  the  opposite  direction,  all  of  which  has  a  tendency  to  reduce  the 
thermal  efficiency  of  the  engine. 

The  quality  of  the  mixture  is  another  matter  of  importance   in 


:  :•  :  :  •„  : 

HORSE  POWER—  Kekit'tfiAs.V  .       V  :*  95 


connection  with  the  efficiency  anS.p^f..oJ;&*.^i»{T£tiXe.Y.  If  the 
mixture  is  rich  in  fuel  gases,  that  is,  if  it  contains  a  large  quantity 
of  heat  units  it  cannot  be  compressed  as  high  as  a  leaner  mixture, 
and  consequently  its  efficiency  will  be  reduced.  Almost  any  gas, 
no  matter  how  lean,  if  compressed  high  enough,  can  be  ignited,  and, 
in  view  of  the  statement  that  efficiency  depends  upon  the  degree  of 
compression,  it  would  thus  appear  that  lean  mixtures  yield  the  higher 
efficiencies.  This  appears  to  be  true  theoretically  and  has  been  worked 
out  and  verified  practically. 

We  made  the  statement  that  the  power  which  might  be  obtained 
at  the  fly  wheel  is  always  less  than  that  expended  upon  the  piston. 
This  is  true  in  the  case  of  the  steam  engine,  but  more  particularly 
true  of  the  gas  engine.  The  difference  between  the  power  supplied 
to  the  engine  and  that  which  may  be  obtained  from  it,  is  used  up 
in  internal  friction.  In  the  case  of  the  steam  engine,  there  is  the 
friction  of  all  the  working  parts  which  may  amount  to  anywhere 
from  five  to  twenty  per  cent  of  the  power  supplied.  In  the  case  of 
the  gas  engine  the  friction  is  considerably  higher,  due  to  the  fact 
that  for  every  four  strokes  of  the  engine  there  is  only  one  power 
stroke.  There  must  be  supplied  by  the  fuel  a  certain  extra  amount 
of  power  to  overcome  the  friction  of  the  three  idle  strokes,  thus 
making  the  difference  between  the  indicated  and  brake  power  much 
larger  than  in  the  case  of  the  steam  engine.  The  very  highest 
efficiency  obtained  from  gas  engines  shows  a  loss  of  at  least  fifteen 
per  cent  in  friction,  while  losses  of  twenty  and  twenty-five  per  cent 
are  common  and  represent  current  practice. 

The  mechanical  efficiency  of  an  engine  is  represented  by  the  ratio 
between  the  brake  horse  power  and  indicated  horse  power;  for  ex-. 
ample,  if  an  engine  indicates  5-horse  power  and  it  shows  4-horse 
power  by  brake  test  at  the  fly  wheel,  its  mechanical  efficiency  is  four- 
fifths  or  eighty  per  cent. 

The  thermal  or  heat  efficiency,  however,  is  a  different  thing  and  rep- 
resents the  proportion  of  the  heat  energy  which  is  transformed  into 
mechanical  energy.  This  is  always  low  and  for  ordinary  medium  sized 
gas  engines  is  in  the  neighborhood  of  fifteen  per  cent.  In  a  few  cases 
thermal  efficiencies  as  high  as  twenty-five  per  cent  have  been  obtained 
for  gasoline  engines,  while  the  very  highest  efficiencies  have  amounted 
to  about  thirty  per  cent.  Where  the  thermal  efficiency  is  twenty- 
five  per  cent  it  means  that  the  heat  value  of  one  hundred  pounds  of 
fuel  is  utilized  or  expended  in  the  engine  to  obtain  the  useful  effect 
of  only  twenty-five  pounds.  There  is,  then,  a  loss  of  three-fourths  of 
the  heat  energy  supplied  to  our  best  gasoline  engines  in  transforming 
the  fuel  into  useful  energy. 


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